Comprehensive Critique of Thomistic Natural Law Ethics Using the Example of Sexual Acts

Foreword

This critique explores Thomistic natural law ethics, using the example of sexual acts to illustrate broader concerns. Thomistic natural law theory always consists—without exception—of three core elements: naturalism, supernaturalism, and intuitionism. The emphasis placed on each component may vary significantly from one Thomist to another.

Importantly, there exists no Thomistic account that is purely and exclusively naturalistic or supernaturalistic. But herein lies a central difficulty: a theory might be composed of, say, 70% naturalism, 25% intuitionism, and 5% supernaturalism. The problem arises when the dominant naturalistic component depends on the seemingly minor supernaturalistic one—for instance, in affirming the sacramental institution of marriage, adopting an anti-hedonistic spiritual attitude, or pursuing a spiritually defined concept of love. If one rejects that 5%—regarding it as implausible or absurd—the entire 70% may lose its persuasive power and internal coherence.

Moreover, Thomistic natural law presupposes a Catholic-Christian moral intuition. Without this underlying intuition, the theory as a whole becomes less convincing, particularly to those outside this specific worldview.

To critique Thomistic natural law, one need only consult a well-regarded handbook of analytic ethics and examine the challenges associated with naturalism, intuitionism, and supernaturalism. Each contains systematic difficulties that have been widely recognized and discussed.

In this critique, my primary focus is on naturalism—and specifically on a version of natural law that emphasizes this element. Such theories often center on the perverted faculty argument, historically championed by Elizabeth Anscombe and, more recently, by Edward Feser.

The topic of sexuality is particularly revealing in this context. Despite denials from some proponents, sexuality remains a central concern for many natural law theorists. In most other domains, natural law ethics can be replaced by alternative ethical systems. In sexual ethics, however, natural law seems to claim a kind of monopoly. At the heart of this dominance lies the perverted faculty argument:

"Natural law thinkers earlier in this century often relied on the 'perverted faculty argument' to demonstrate the moral illicitness of various sexual practices, prominently including contraception. According to that argument, procreation is the natural function of semen, of the human genitalia, or more generally of the ‘reproductive faculty.’"
—Paul J. Weithman, Natural Law, Morality, and Sexual Complementarity

That said, it's worth noting that many contemporary defenders of Thomistic natural law have moved beyond this framework:

"The best recent defenders of a Thomistic natural law approach are attempting to move beyond it [the perverted faculty argument]."
—Brent L. Pickett, Natural Law and the Regulation of Sexuality: A Critique

We can therefore distinguish at least two broad camps within the Thomistic natural law tradition:

1.     Teleological approaches, emphasizing the physical structure and ends of human nature (e.g., traditional Roman Catholic arguments against contraception).

2.     Rationalist approaches, which focus instead on the nature of practical reason and its moral implications (e.g., the work of Finnis, Grisez, Boyle, or Gomez-Lobo).

As Kevin Wm. Wildes notes:

"Some approaches to natural law have emphasized the physical structure of nature... Other approaches to ‘nature’ focus more on the nature of practical reason rather than the teleology of natural physical structures."

Importantly, the "structure" of human nature should not be interpreted merely in physical or outward terms—that would be crude and superficial. Rather, it includes a felt, internal dimension, an inner moral significance that must be accounted for.

To summarize, natural law ethics maintains a basic premise:

Acting contrary to nature is morally wrong; acting according to nature is morally right.

Yet what counts as “nature” is subject to vastly different interpretations. Every definition of nature already presupposes particular views about moral reasoning and value hierarchies. This variability has led some scholars to describe natural law not as a single theory, but rather as a broad and pluralistic tradition of ethical inquiry. As Harry J. Gensler writes:

"Natural law is more a broadly pluralistic tradition of doing ethics than a precisely formulated ethical theory... Some in the natural-law tradition base ethics on God’s will (supernaturalism), others on empirical facts about desire (naturalism), and still others on self-evident moral truths (intuitionism). But all claim to follow the inspiration of St. Thomas Aquinas."

Most natural law thinkers are non-consequentialists, defending exceptionless moral norms—for example, prohibitions against killing the innocent. Some, however, embrace proportionalist views or develop virtue ethics within the natural law tradition.

Closing Remark

"The fact that there are numerous theories of natural law, some at great variance with one another, indicates that moral truth may not be as easily apprehended as proponents have asserted."
—Kevin Wm. Wildes, S.J., Whose Nature? Natural Law in a Pluralistic World

I. Central Objections to Classical Thomistic Natural Law Theory

One of my fundamental concerns with classical Thomistic natural law lies in its apparent incompatibility with the Christian doctrine of original sin—or indeed with any form of philosophical pessimism. If human nature is marred by sin, even essentially so, how can it serve as a reliable standard for moral action? Why should I strive to act according to a nature that is, in its totality, sinful?

This concern is not merely academic. Consider the perspective of many biblically oriented Christians, for whom nature is not a moral guide but part of a fallen order:

“For the Christian, however, nature is not the standard, because the world of nature is a fallen world, a world in rebellion against God and infected by sin and death. For a standard, we must look beyond nature to God.”
— Darash Press

Even Aristotle, whose work undergirds much of Thomistic ethics, wrote that “nature is demonic, but not divine” (De Divinatione 2, 463b 15).

This raises critical questions: How far does sin extend? Is all of human nature corrupt, or only certain faculties? Does sin infect everything except the rational soul, as some theologians claim? These questions remain unanswered in the work of prominent Thomists like Edward Feser—or at least, I have found no substantial engagement with them. Feser, I suspect, silently adopts a Pelagian view of human nature that downplays inherited original sin. While Catholic doctrine officially adheres to a semi-Pelagian compromise, I would argue that this position is philosophically incoherent, resting on a fallacy of the middle ground.

Indeed, natural law seems only compatible with Pelagian or semi-Pelagian optimism. Augustine, on the other hand, maintained that all of nature was corrupted by original sin. In this light, natural law ethics begins to look heretical, at least from an Augustinian standpoint. I might have said more on this point, but the concept of original sin is itself vague and frequently invoked by theologians as a philosophical escape hatch—a move made precisely when other arguments fail.

Self-Deception and the Nature of Human Nature

The sociobiologist Robert Trivers offers a striking challenge to natural law optimism. In his book The Folly of Fools, Trivers argues that humans possess a biologically ingrained capacity for self-deception—a trait that evolved precisely to make lies more convincing to others. If this faculty is natural, then what does that mean for natural law? Would the Church reject this as a sinful deviation? Or would it accept it as part of our God-given nature? I am unsure. But I do know this: if the natural lawyer conveniently labels every morally inconvenient trait as “sinful,” this begins to look like theological evasion.

In this regard, Fritz Mauthner was absolutely correct when he wrote:

“All natural law scholars were and had to be: optimists, thus bad Christians; they believed in the goodness of human nature.”
— Fritz Mauthner, Wörterbuch der Philosophie (my translation)

Indeed, natural law presupposes philosophical optimism: that human nature is fundamentally good, that life is worth living, and that procreation is a moral good. But this is not a logical conclusion—it is a subjective disposition. Whether one is an optimist or a pessimist is not something that can be proven. Natural law, therefore, rests on a weak foundation, one that fails to persuade pessimists or antinatalists.

Can one who shares Alexander von Humboldt’s radical skepticism about human life be a natural law theorist?

“I regard marriage as a sin and the propagation of children as a crime.”
— Alexander von Humboldt

Aristotle, Subjectivity, and the Ambiguity of Human Nature

Even Aristotle, while not concerned with subjectivity in the modern sense, comes close in his discussion of anger. He describes the form of anger as the emotional experience itself, and its matter as the physical bubbling of the blood. But anger, of course, also involves behaviors like slamming a fist on the table or verbal aggression. Crucially, every emotional form in Aristotle’s framework is goal-directed—implicating final causality and, by extension, natural law relevance.

If so, Emmett Barcalow’s critique becomes especially potent:

“It may be that human beings, or at least male human beings, are naturally aggressive and prone to violence... Should men act in accordance with their inherent nature, or should they resist it?”
— Emmett Barcalow, Moral Philosophy: Theories and Issues

Likewise, if children are naturally cruel—delighting in the suffering of others—does that mean cruelty is natural, and therefore morally acceptable? And if humans are naturally self-interested, should altruism be rejected as unnatural? These questions point to a basic tension in natural law theory: is everything natural morally good? And if not, how do we distinguish the morally relevant parts of nature from the morally irrelevant or corrupt ones?

The Gewirth-Nielsen Objection: What Counts as ‘Natural’?

Alan Gewirth makes a similar observation:

“If we identify man’s good with his nature, and his nature includes lying, cheating, and the Oedipus complex, then these must also be part of man’s good. But these conclusions are morally unacceptable.”

This highlights the arbitrariness of many natural law claims. Thomists often define “natural inclinations” in a circular way: inclinations that align with Catholic doctrine are “natural,” while those that contradict it are labeled “unnatural” or “disordered.”

Kai Nielsen makes this critique explicit:

“To rule out some natural inclinations as corrupt or sinful indicates that we are using a criterion in moral appraisal that is distinct from the natural law criterion itself. In practice, natural law is simply Catholic morality dressed up as metaphysics.”
— Kai Nielsen, Atheism and Philosophy

Is Evil Merely the Absence of Good?

Finally, many Thomists fall back on the classical doctrine that evil is not a substance but merely the absence of good (privatio boni). This view, however, is far from self-evident and carries with it deep philosophical problems.

Consider two interpretations:

1.     Optimistic reading: If evil is nothing real, then we might conclude that there is no actual evil in the world—only the absence of good. This makes moral violations of natural law conceptually impossible.

2.     Nominalist reading: The phrase “absence of good” is simply a semantic variation on “evil,” with no explanatory power. To say “I do evil” is functionally identical to saying “I act in the absence of good.” Nothing is gained here except terminological confusion.

Worse still, if evil is not real, then why are the Ten Commandments expressed as negations? ("Thou shalt not kill,” “Thou shalt not commit adultery,” etc.) What are we being told to avoid if evil does not positively exist?

II. The Is-Ought Problem in Natural Law Theory

One of the most persistent challenges to natural law ethics—especially in its classical Thomistic formulation—is the well-known is-ought problem. It raises the question: Can a moral obligation ("ought") be validly derived from a description of what is the case in nature ("is")? This issue proves especially troubling for those who attempt to ground ethics in teleological features of human biology.

Natural law theorists frequently argue that because human organs and faculties are functionally or teleologically structured, we can infer how they ought to be used. But this inference is logically flawed. The fact that digestion has a function, or that the reproductive system is structured toward procreation, does not by itself imply a moral obligation to eat or procreate in specific ways. These are natural processes, not commands.

As Robin Gill aptly summarizes:

"To derive an exclusive moral prescription from an empirical observation of function is to commit a category error."
— Robin Gill, A Textbook of Christian Ethics

This is the very point David Hume emphasized: you cannot derive an "ought" from an "is". Even if nature exhibits a kind of unconscious teleology—as in Aristotelian biology—these structures remain non-personal and non-prescriptive. They describe how things work, but not how people ought to act.

Let’s take a thought experiment: If the world were, as Nietzsche described, merely a battlefield of competing wills to power, even a Thomist would likely concede that no moral obligations could be derived from such a nature. If we imagine the soul thrown into a world devoid of objective values—only drives and instincts—natural law reasoning breaks down. And yet, it continues to assert an ethical authority from nature alone.

The Necessity of a Willing Other for Moral Obligation

What, then, grounds an “ought”? I submit that a moral obligation only arises in the presence of another rational will. An "ought" is relational; it presupposes a demand, a normative appeal from one person to another. Whether this will is human, angelic, demonic, or divine, what matters is its personhood and intentional demand.

This is the only plausible grounding of normativity. The Thomist must, if he wishes to remain philosophically credible, accept this.

Three illuminating quotations make the point:

“A good rule of thumb for understanding the practical ‘ought’ is: Where there's an ‘ought’, there's a will of someone else. If A ought to do X, it implies that someone wants A to do X.”
— Peter Stemmer (my translation)

“Ought expresses a necessity, which, however, is not given by objective conditions, but always includes the will of a foreign instance... most often a person.”
— Buscha & Helbig, German Grammar (my translation)

“Such an ‘ought’ is nothing but the synthetic result of the encounter of subjects, each of whom is a conscious willing being in relation to the other.”
— Gerold Prauss, Moral and Law in the State (my translation)

For example: If someone turns to me and says, "Help me, please", I immediately recognize the moral significance—not because of biology, but because a person is making a demand of me. Her will becomes, in my mind, an ought. This is the essential mechanism: we translate another’s will into our obligation.

God and the Hidden Divine Command Theory in Natural Law

This analysis reveals something critical: Natural law ethics must presuppose a divine will if it is to generate moral obligations at all. But this introduces a tension. In classical natural law, God is often not presented as a personal lawgiver in the style of divine command theory—but He must be. Only the will of a rational agent can generate moral force. This is why Francisco Suárez argued that natural law derives its binding character from God’s legislative act:

“For a law to be genuine law and not just law in name, it must be grounded in the legislative act of a superior. The obligatory force of natural law comes from God’s will.”
— Francisco Suárez, via IEP

This makes clear: without divine command, natural law lacks binding power. But if that’s the case, then natural law is not autonomous—it is simply a veiled form of divine command theory.

And yet, God does not communicate moral obligations clearly through the design of our faculties. Why should God address me via my organs or impulses rather than through my conscience—as understood in traditional Christian theology? The claim that final causality expresses divine will is, at best, ambiguous, and for nonbelievers, it is utterly unconvincing.

If God Doesn’t Exist, Natural Law Collapses

Without belief in a personal God, natural law theory faces immediate collapse. As Hume’s guillotine takes effect, any attempt to derive moral duties from natural facts becomes a fallacy.

As Kai Nielsen explains:

“Those who think they can discover what they ought to do from a discovery about the ‘ultimate nature of reality’ are tacitly assuming that what is metaphysically real ought to be. But this is not logically necessary, or even plausible.”
— Kai Nielsen, “An Examination of the Thomistic Theory of Natural Moral Law”

Even for agnostics, this "indirect communication" from God via biology is insufficient. If God truly wished to communicate, why would He do so via ambiguous signals encoded in bodily functions? A divine manual—explicit, universal, direct—would be required. In its absence, we’re left guessing at divine intention.

The Arbitrariness of Nature as a Moral Guide

Even if we accept God’s existence, new problems emerge. God, being omnipotent, could have created any nature—and with it, any corresponding morality. He could still override current nature with miracles or redesigns. Why should we assume that the teleology of our organs corresponds to His moral will?

Moreover, why should God’s will be binding at all, given His non-participation in worldly suffering? The idea that God's will is ipso facto good is itself a value judgment, not a rational conclusion. This is the dilemma raised by the Euthyphro problem and echoed by critics like the Marcionites or Gnostic thinkers who viewed the creator of the world as possibly malevolent.

Even Germain Grisez, a conservative natural law thinker, admits:

“It is not evident that God requires that this design [of human nature] always be respected.”
— Germain Grisez, “Contraception and the New Natural Law”

And what about non-human nature? If I see a beetle struggling on its back, its teleological striving expresses a “design.” Am I morally obligated to help it? If a fly, acting according to its nature, annoys me and I kill it—have I violated a divine will?

To arbitrarily declare that only human teleology is morally relevant, the Thomist must offer more than assertions. Otherwise, the theory is just species-specific metaphysical bias.

Entropy, Stones, and the Absurdity of Universal Teleology

Consider entropy—the cosmic tendency toward disorder. It is arguably the most universal teleological process observable. If nature’s purpose is to reach maximum entropy, does that mean we are morally obligated to assist the universe in dying?

Similarly, Aristotle claimed that a stone’s natural place is on the Earth. If that’s true, would it be immoral to throw a stone into the air?

These examples expose the absurdities that arise when one treats teleology as a sufficient moral guide.

The Thomist Bypasses the Is-Ought Problem by Smuggling in Consequences

Ultimately, the Thomist does not resolve the is-ought problem—he sidesteps it. In his framework, you may act contrary to nature, but you must suffer the consequences: heaven or hell. This is not moral reasoning but metaphysical consequentialism masquerading as virtue ethics.

In effect, God becomes a theological utilitarian: concerned with maximizing the number of souls in heaven, minimizing those in hell. But this, too, rests entirely on faith, not reason.

Closing Critiques

Let us conclude with a few powerful quotes that reinforce the is-ought dilemma:

“To discover what our natural inclinations are is to discover a fact. But that we ought to have these inclinations or act on them does not follow.”
— Kai Nielsen

“Even if one could exhaustively describe human nature, the claim that we are morally obliged to act in accord with it is something additional—not a conclusion of fact but a presupposition of value.”
— David Bentley Hart

“Feser claims that reason seeks the good, so there is no is-ought gap. But the gap remains—between what nature intends and what we should do.”
— (Anonymous Internet Commentator)

III. The Epistemological Problem of Recognizing Natural Law

1. The Hylomorphic Challenge: Body and Mind as a Unity

If body and mind together form a genuine hylomorphic unity, as classical Aristotelian-Thomistic metaphysics claims, then physical and mental processes mutually influence each other. This raises a fundamental epistemological question: How can we trust our insight into natural law, if both body and mind are susceptible to disturbance?

What if someone believes they understand natural law but suffers from a mental disorder or bodily illness? How much confidence should we place in their judgment? Both conditions can distort perception, reasoning, and emotion. For example, a person blind from birth develops a unique relationship to reality—raising questions about the extent to which sensory input (especially vision) shapes the natural law theorist’s conception of human teleology. Naturalistic Thomists seem especially reliant on vision when appealing to the physical “design” of nature.

Consider also a manic-depressive individual, perhaps deeply religious. Can we still trust their ethical insight? Political discourse offers parallels—left- and right-wing thinkers often diagnose the opposing side as ideologically or psychologically diseased. In doing so, they implicitly deny the opponent a valid perception of human nature.

2. Cultural and Traditional Biases

Cultural norms, traditions, and religious customs can easily cloud our ability to objectively discern human purpose. Take, for example, circumcision: embraced by certain religions as morally acceptable, even essential, it is by natural law standards a form of genital mutilation—a practice contrary to the teleological integrity of the body. But long-standing religious tradition has rendered this ethical violation invisible to its adherents.

What if Western culture too is affected by such distortions? What if patriarchy, modernity, or postmodernity have obscured certain natural truths? Could it be that only Thomists see clearly? Or are they themselves victims of their own cultural framework?

If natural law can be so easily obscured by a "thin cultural veil", as your metaphor suggests, then its epistemic reliability becomes questionable. What if, instead of guiding us, our reproductive organs are actually moral tests, meant to be resisted? Who can truly tell? The ease with which natural law can be masked undermines its claim to universal clarity.

3. Accountability and the Limits of Knowledge

Does my inability to recognize divine order relieve me of moral responsibility? If I violate natural law due to ignorance or false belief, am I accountable? These are not peripheral concerns, since natural law ethics presupposes access to truth about human nature.

Even in ideal circumstances—i.e., with a healthy body and mind, and a neutral scientific viewpoint—recognizing purpose in nature remains fraught. As Robert Spaemann (interpreting Aristotle) points out:

“The more matter is involved in the formation of an object, the more unclear its purpose becomes for the scientist.”

Alan Gewirth echoes this difficulty:

“Aristotle showed that there is no simple way of equating the essential nature of a species with any of its observable features—be it matter, form, function, or genus.”

Are we then to consult zoologists and anatomists to discover human purpose? If so, natural law becomes dependent on empirical science, and therefore vulnerable to falsification.

4. Science versus Natural Law: Falsification and Revision

Historically, the Church has had to revise its moral teachings based on new scientific findings. One example is the Church’s long-standing condemnation of the female-superior sexual position, deemed unnatural because it allegedly impeded conception. Later anatomical insights disproved this, forcing the Church to quietly withdraw its objection.

As T.M. Murray observes:

“The facts are revisable in ethics for the same reason they are in science—our knowledge evolves. Therefore, ethical conclusions must remain provisional.”

Germain Grisez admits that older scholastics misunderstood female physiology, leading to faulty moral judgments. Their conclusions about masturbation, for instance, were built on flawed empirical assumptions.

Or consider the long-held belief in the biological subordination of women. Aquinas was adamant that women were “defective males,” a view rooted in the now-outdated science of his day. As David Berger—a gay Thomist expelled by the Catholic Church—notes:

“Aquinas claimed women were failed men produced in warm, humid climates. Today, no faithful Thomist would defend this—but many of the conclusions derived from such ideas remain suspiciously intact.”

If natural law can produce false moral conclusions based on outdated science, what confidence can we place in it today?

5. The Problem of Moral Epistemology: Can We Ever Know Natural Law?

Even if absolute natural law exists, how could we ever know that we’ve truly discovered it?

This is the central epistemological objection. Anthony J. Lisska concedes that Aquinas was nearly agnostic about our ability to know essences. He cites Aquinas himself:

“The essential principles of things are unknown to us.”
— De Anima I, lec. 13

“We do not know even the essence of a fly.”
— In Symbolo Apostolorum I

If we cannot comprehend the essence of a fly, how can we claim certainty about the essence of human sexuality—one of the most context-sensitive and culturally entangled aspects of human nature?

Jacques Maritain, a major neo-Thomist, attempts to salvage moral epistemology by appealing to mystical intuition. He argues that we “know” natural law not through concepts, but through inclination or connaturality. But as Kai Nielsen rightly points out, this notion is deeply obscure:

“This so-called ‘knowledge through inclination’ seems more like a feeling or attitude than actual knowledge. To call it knowledge is to render philosophical evaluation impossible.”

The appeal to mystical intuition replaces rational ethics with private sentiment, leaving us with no way to distinguish true insight from cultural indoctrination or psychological projection.

6. Natural Law as Ideological Projection

As Robert Anton Wilson satirically notes, Natural Law often becomes a metaphysical smokescreen:

“The Natural Law theorist speaks of abstractions with capital letters... If the hypnosis works, these abstractions seem more real than a ham sandwich.”

And further:

“Natural Law is a spook in Stirner’s sense—a disguised metaphysics through which people rationalize personal prejudices.”

In short, natural law functions as a rhetorical device, granting divine authority to one’s own moral intuitions—often without recognizing the cultural, historical, or psychological forces shaping those intuitions.

7. Aristotle’s Epistemological Incoherence

Even Aristotle struggled with the recognition of essences. To guarantee their knowability, he had to push his theory toward a speculative dualism, elevating the intellect (nous) to a quasi-divine status. This move disrupted his own hylomorphic framework, as Wolfgang Welsch notes:

“Aristotle’s soul theory failed to gain influence because it couldn’t integrate the mind into his body-soul concept. This gap later paved the way for Cartesian dualism.”

As J.L. Ackrill observes:

“If pure thought requires no physical organ, then nous must exist separately. But Aristotle provides no clear account of this disembodied activity.”

Even within Aristotle’s own system, then, the mind stands apart, making the reliable perception of natural purposes an unresolved metaphysical puzzle.

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Conclusion: Natural Law’s Epistemological Weakness

Natural law, if it exists, remains epistemologically opaque. It is susceptible to mental and physical distortion, cultural bias, scientific revision, theological mythologizing, and conceptual mystification.

The final blow comes from Epicurean ethics: If God is morally indifferent to us (as the lack of clear communication suggests), then we can be morally indifferent to Him and to His alleged laws.

To summarize the central objection:

Even if natural law exists, we could never know if we had found it—and therefore it cannot serve as a reliable moral guide.

IV. Is Natural Law Compatible with Evolutionary Theory?

In an age of dominant scientific paradigms and widespread secularism, one of the most pressing questions for Thomistic natural law ethics is this:
Can natural law be reconciled with the theory of biological evolution?

To examine this question, we must first understand what evolution implies about human beings and their nature.

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1. Human Nature in the Context of Evolution

At its core, evolutionary theory claims that the structure and features of human nature are the result of morally neutral adaptations. These adaptations—arising from the propagation of "selfish genes"—proved more successful than competing traits in the distant past. Evolution, moreover, is not a completed process; it continues through sexual selection, often shaped by arbitrary and amoral criteria of attractiveness and survival.

Imagine a hypothetical mutation that causes individuals to grow a third arm. Initially dysfunctional, this extra limb might be sexually appealing, and over generations, sexual selection might favor it—eventually leading to its full integration into human anatomy. This scenario could apply to any trait—physical, psychological, or behavioral. Evolution does not recognize moral boundaries.

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2. The Problem of Fixed Species: The End of Aristotelian Essentialism

A key result of evolutionary biology is the rejection of fixed, sharply defined species. Life does not conform to neatly bounded categories. Instead, species emerge from a continuous, gradual process of change and adaptation. As Richard Dawkins and Ernst Mayr explain, the concept of a “typical” member of a species is a statistical abstraction, not a biological reality.

“There is no permanent rabbitiness... just a distribution of variations.”
— Richard Dawkins, The Greatest Show on Earth

Aristotle’s notion of species as immutable natural kinds—each defined by an essential form or eidos—has become untenable. Biological essentialism, as traditionally held by creationists and Aristotelians alike, assumes that each species possesses a fixed nature, separable from others by sharp boundaries. But evolutionary theory, especially in its modern gradualist form, renders this view obsolete.

“The real world consists only of individuals who are more or less closely related to each other by virtue of descent from one or more common ancestors.”
— Michael Hauskeller

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3. Evolution vs. Fixed Moral Norms

If human nature is constantly evolving, then it cannot serve as an eternal and universal basis for moral norms. Thomistic natural law assumes a fixed, essential human nature:

“Aquinas believed that all human beings have a fixed, uniform human nature – this led him to maintain that there was a fixed natural law for human beings.”
— Peter Vardy

But if there is no precise point at which man becomes man, and if traits arise and disappear through random mutations and shifting selection pressures, then what grounding can natural law have? Evolution undermines the very possibility of identifying stable essences—which natural law ethics requires for its universal moral prescriptions.

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4. Moral Ambiguities in Evolutionary Adaptation

Evolution has no inherent moral direction. It is brutal, contingent, and indifferent to human ideals. Traits emerge based on survivability, not virtue. Evolution rewards reproductive success, not moral excellence.

Should natural law then follow evolutionary trends to remain relevant? If so, it becomes relativistic. But if it resists evolution, then it becomes disconnected from biological reality. Either way, its credibility suffers.

Even seemingly immutable aspects of our biology—like reproductive organs or sexual orientation—are subject to change. For instance, homosexual behavior, long condemned in Thomistic ethics, appears naturally in human populations and may even serve evolutionary purposes such as kin selection or population control.

“Homosexuals are simply individuals whose erotic tendencies have shifted. From a population perspective, this is still entirely natural.”

“It could be (and there is no evidence for this) that in the face of an overcrowded world, nature produces an increase in those genes which direct sexual activity away from procreation.”
— Peter Vardy

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5. Reproductive and Sexual Behavior in Evolutionary Light

Modern evolutionary psychology provides plausible models for previously taboo behaviors. For example:

• Contraception has evolutionary analogues in the animal kingdom, such as sperm-selecting females or ingestion of fertility-blocking plants.
• The male penis may have evolved not just for insemination but also to displace rival semen—suggesting natural promiscuity.
• The loss of interest in a sexual partner after intercourse could be a product of selection for genetic diversity.

Books like Sex at Dawn argue that monogamy is unnatural, and our species evolved in polyamorous, egalitarian sexual groups.

These insights conflict sharply with the rigid sexual ethics of natural law, which presumes a divinely instituted teleology of heterosexual, procreative, monogamous union.

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6. Evolution and the Collapse of Thomistic Essentialism

If evolution is real, then we are forced to abandon species essentialism. This has direct consequences for ethics. In Thomistic natural law:

• What is morally good is what corresponds to the fixed essence of a thing.
• What is bad or disordered is what deviates from that essence.

But in evolutionary thinking:

• What is good is what is adaptive.
• What is disordered is merely less reproductively successful, not immoral.

These are two radically different frameworks. Thomistic ethics judges value by correspondence to a fixed form; evolution judges fitness by contextual functionality.

Moreover, evolution affects not only external traits, but also internal dispositions and behaviors. What once seemed maladaptive may become adaptive—and vice versa. Evolution knows nothing of eternal norms.

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7. The Theological Consequences of Evolution

From a theological perspective, further problems arise. Thomists hold that God infuses an intellectual soul into each human embryo. But this genetic material is itself the result of an amoral and bloody evolutionary history. How can such material serve as a moral standard?

Accepting evolution also forces one to reframe God as a divine tinkerer—creating through a trial-and-error process rather than through fixed, intentional designs. This raises the uncomfortable possibility that natural law morality is based on the contingent products of blind mutation—hardly a firm foundation for eternal ethical principles.

As Michael Hauskeller points out, even if one retains the concept of telos (purpose), it must shift from a species-wide good to an individual good:

“The good Aristotle talks about is not the good of the species, but the good of an individual.”

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8. No Middle Ground: Thomism vs. Evolution

Ultimately, natural law theorists face a dilemma:

• Either they reject the theory of evolution and become covert creationists;
• Or they accept evolution but abandon the idea of eternal moral forms.

Even if they adopt punctuated equilibrium (Gould) rather than gradualism (Dawkins), the Aristotelian idea that no “eternal species” can give birth to another “eternal species” remains incompatible with any evolutionary framework.

And even if one accepts a divinely guided evolution, one must explain why nature appears so directionless and why morality seems so fluid and context-dependent.

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9. Conclusion: The Unbridgeable Divide

The ethical implications of evolution are incompatible with conservative Thomistic natural law ethics. A theory of morality based on fixed, universal essences cannot coexist with a biological reality shaped by contingency, variation, mutation, and adaptation.

Under evolutionary assumptions:

• Species are not real kinds, but statistical groupings of individual variation.
• Essential traits blur into accidental ones.
• Behavior and purpose shift over time.

If morality is to evolve with life, then natural law cannot remain static. But if morality is static, then it must divorce itself from nature, rendering the term "natural law" incoherent.

To salvage natural law in an evolutionary framework, one would need:

1.     A clear proof of God's existence;

2.     A conceptually coherent account of free will;

3.     A non-essentialist metaphysics of moral normativity;

4.     And a flexible, dynamic ethics that adjusts with the evolution of life.

But these conditions are not currently met. Until they are, natural law ethics remains suspended in mid-air, supported only by faith and metaphysical nostalgia.

“Since the concept of free will is extremely problematic and no proof of a monotheistic God is ultimately convincing from a religiously neutral perspective, every natural law ethics is, for better or worse, in a state of suspense.”

II.1) Alternative Interpretations of Human Essence

The essence of man can be interpreted in ways that are arguably deeper, broader, and more philosophically convincing than Aristotle's conceptualization. Four particularly radical interpretations shall serve to illustrate this possibility:

1.     As Blind Will to Live (Schopenhauer)
According to Arthur Schopenhauer, the essence of human existence is the blind, instinctual will to live. The primary aim is the preservation of life and reproduction, without higher teleology or final cause. As Christopher Janaway summarizes:

"The will has no overall purpose, aims at no highest good. Although it is our essence, it strikes us as an alien agency within, striving for life and procreation blindly, mediated only secondarily by consciousness. Instinctive sexuality is at our core, interfering constantly with the life of the intellect."
(Christopher Janaway, Willing and Nothingness)

For Schopenhauer, even conscious willing is just one manifestation of a more fundamental, unconscious striving. The body itself is the will objectified, and all natural processes, from digestion to sexual arousal, are expressions of this blind force. Science, for Schopenhauer, fails to grasp this inner nature and merely describes phenomena. The ethical conclusion he draws is not a celebration of nature, but its denial: quietism, asceticism, and ultimately, the negation of the will.

2.     As Blind Will to Power (Nietzsche)
Friedrich Nietzsche radicalizes Schopenhauer's notion by claiming the will to live is subordinate to a more fundamental will: the will to power. All life, according to Nietzsche, seeks to grow, dominate, and impose its form upon others. Morality itself becomes a vehicle of this will:

"Everything that enhances people’s feeling of power, will to power, power itself."
(The Anti-Christ)

Nietzsche rejects the Stoic ideal of "living according to nature" as self-deception. Life, he insists, is inherently about appropriation, transformation, and overcoming. There is no fixed meaning or telos, only a constant reinterpretation of phenomena by superior wills. Even biological functions like procreation and nutrition are subsumed under the will to power, whose expressions include domination, transformation, and revaluation of values. Nature is not a norm; it is a battlefield.

3.     As Blind Will to Death (Mainländer)
Philipp Mainländer offers a metaphysical inversion of Schopenhauer. While accepting the idea of a blind will, he reinterprets its ultimate aim not as life, but as death. Life is merely the means through which God, having once existed, dies by fragmenting Himself into a multiplicity of beings, each striving unconsciously for non-being:

"God is dead and his death was the life of the world."
(Mainländer, Philosophy of Redemption)

All activity and striving ultimately aim at the dissolution of the self and the cosmos. This metaphysical pessimism renders all affirmations of life morally suspect. The ethical ideal becomes voluntary self-dissolution and rejection of procreation. Even modern physics with its ideas of entropy and heat death appears, to some, to echo Mainländer's metaphysical vision.

4.     As Seeing Will for Value (Weininger)
Otto Weininger, unlike the previous thinkers, identifies the essence of man with a metaphysical striving toward truth, value, and logic. Drawing from Kantian ethics, he sees man as a moral being whose highest calling is to become autonomous and rational:

"Duty is only duty to oneself, duty of the empirical ego to the intelligible ego."
(Weininger, Sex and Character)

Kantian moral law, for Weininger, is rooted in pure reason and must not be derived from human nature, emotion, or any empirical source. The categorical imperative, as an expression of internal moral law, is incompatible with utilitarianism or nature-based ethics. Weininger also advocates sexual abstinence as a metaphysical ideal, arguing that procreation instrumentalizes the other and is therefore immoral.

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Each of these interpretations leads to ethical frameworks radically at odds with Thomistic natural law. Schopenhauer finds the will-to-live inherently immoral. Nietzsche sees moral systems as expressions of power structures. Mainländer proclaims death as the goal of life. Weininger posits an ideal, ascetic rationalism rooted in logic and self-responsibility.

Thomistic natural law presupposes philosophical optimism: that human nature is fundamentally good and purposeful. Yet this optimism is hard to reconcile with doctrines such as eternal damnation or original sin. Even Socrates, as Ehrman notes, regarded death (conceived as non-existence) as potentially a great good. David Bentley Hart argues compellingly that mere existence without well-being is not a gift, but a burden.

These alternative accounts destabilize natural law's foundations. If the essence of man is not fixed, rational, and teleologically good, but blind, self-destructive, or metaphysically strained toward a non-natural ideal, then deriving morality from nature becomes untenable. The ethics of natural law require a concept of nature as stable, normative, and inherently good. None of the above systems affirm this.

Hence, a commitment to natural law is inseparable from metaphysical assumptions about the nature of being, of will, and of purpose. When these assumptions are challenged by alternative models, the coherence and authority of natural law come under critical pressure.

II.2) The Basic Idea of Natural Law in Relation to Sexuality Is Not Very Plausible

Catholic Thomists assert the following principle with great confidence and ethical weight: Every sexual act (understood here as any sensual act involving potential ejaculation) must have procreation as its sole indispensable primary purpose. For simplicity, we will consider only potentially fertile sexual acts, setting aside sterile ones.

To Thomists, this claim is self-evident—an axiom. Yet even some Catholic thinkers, such as Germain Grisez, acknowledge that it is neither obvious nor easily demonstrable. In the Thomistic framework, reproduction is the definitive purpose of sex; all other aspects—such as foreplay, emotional bonding, or pleasure—are considered merely incidental or secondary. While they may be acknowledged as “purposes,” they are permitted only as optional means serving the one true end: reproduction.

Questioning the Exclusivity of Reproductive Purpose

But how can one be certain that ejaculation must occur solely within the vagina for the purpose of reproduction? Why should we exclude the possibility that sexuality might serve other natural, primary purposes? The mere fact that vaginal ejaculation can lead to reproduction—though relatively rarely—does not prove that procreation is the only natural end of the sexual act.

It is conceivable that there are natural expressions of sexuality outside of reproduction that fulfill their own legitimate purposes. Thomists cannot logically rule this out. At best, they might say: “Perhaps there are such purposes, but since I cannot clearly perceive them, and only see the reproductive one, I choose to avoid moral risk by ignoring the others.” Fair enough. But if such other purposes do exist, they cannot be said to frustrate the reproductive end, since it is no longer the relevant goal in that context. When another purpose is rightly pursued, reproduction becomes—at most—secondary or optional.

Lessons from the Animal Kingdom

This becomes even clearer when we look to the animal kingdom, which Aquinas himself often referenced. Among many species, sexual behavior is not solely oriented toward reproduction. Masturbation and homosexual behaviors are common and do not result in procreation. In fact, such acts often result in wasted ejaculations—as in the case of orangutans.

An especially illustrative example is the Cape ground squirrel, whose males engage in autofellatio—oral self-stimulation—after mating. According to researchers, the purpose is hygienic: it cleanses the reproductive tract and reduces the risk of sexually transmitted infections.

Source: National Geographic - Squirrels Masturbate to Avoid STIs

Imagine, by thought experiment, that such a squirrel were suddenly endowed with reason—“a soul from outside,” as Aristotle might put it. Would we accuse this squirrel of sinning by misusing his sexual faculties? Hardly. His act served a different, biologically valid purpose: cleanliness—not reproduction. To call this a moral failing would be absurd.

Bonobos and Social Cohesion

Similarly, rational female bonobos might justify their non-reproductive sexual behaviors—such as clitoral stimulation between females—not as contrary to nature, but as contributing to social bonding and the reduction of tension. These, too, are natural and teleologically defensible goals. Even Aquinas acknowledged the value of sociability as a higher good.

If one objects that animal behavior should not serve as a moral model, then Aquinas should refrain from citing it as evidence for natural law. Instead, one must examine human anatomy and physiology, which—according to Andrew Sullivan—offers no indication that nature strictly enforces the reproductive goal.

Andrew Sullivan’s Critique

Sullivan argues that even a “perfect” Catholic couple, fully obedient to natural law, will necessarily engage in non-procreative sex. For example, after conception, all subsequent sexual acts during pregnancy are, by definition, non-reproductive. The male body, however, continues producing sperm. Even in abstinence, nocturnal emissions occur, governed by neurological and hormonal mechanisms. These natural events clearly contradict the strict natural law framework—unless we absurdly call the male body itself sinful.

“Any reasonable account of human sexuality would conclude that even under the strictest Catholic teaching, most sexual activity between a man and a wife must necessarily be non-procreative.”
– Andrew Sullivan, The Conservative Soul

Sullivan highlights the overwhelming biological fact: virtually all sperm are wasted. If nature is our guide, then reproduction appears less like a singular purpose and more like one rare outcome among many possibilities.

Robin Gill and John Noonan: Nature Is Not Always Fertile

The Christian ethicist Robin Gill also notes that events preventing reproduction—such as nocturnal emissions, infertility during much of the menstrual cycle, and spontaneous miscarriage—occur frequently and spontaneously. They are thus “natural” and should not be seen as violations of purpose.

Similarly, John T. Noonan observes that the union of fertility and intercourse is “normal” only on four days per month. He concludes that nature itself has designed the human body so that many sexual acts will be sterile, and using contraception during infertile periods does not violate natural law—because no fertile possibility was present to begin with.

Evolution, Teleology, and Multiple Purposes

If one accepts evolution, then the idea that natural faculties can only have one immutable purpose becomes highly questionable. As with artifacts (e.g., a Swiss army knife used for different purposes in different contexts), natural faculties may also fulfill different primary purposes depending on context. A knife can be used for eating, carving, threatening, or even display. Why should natural functions be more rigid than man-made tools?

Do Thomists allow for any natural faculty to have multiple distinct primary ends depending on the situation? If so, why is sexuality excluded from this flexibility?

Even Kant, known for moral rigidity, accepted a role for casuistry—allowing contextual exceptions in moral reasoning. Aquinas, too, conceded that while natural law’s primary precepts are immutable, its secondary precepts may vary with circumstances. This opens the door to proportionalism, or even a form of situation ethics, within natural law itself.

“The more you descend into the details, the more it appears how the general rule admits of exceptions, so that you have to hedge it with cautions and qualifications.”
– Thomas Aquinas, Summa Theologiae

Toward a Plurality of Natural Sexual Ends

In my view, sexuality serves at least three equally natural and primary purposes, in addition to reproduction:

1.     Emotional bonding and intimacy

2.     Spiritual or transcendent experience

3.     Physical and emotional compatibility testing

These are not far-fetched or eccentric. They correspond to real, common-sense human experiences. Hindu traditions, as well as some Western thinkers, recognize sex as a spiritual practice. The philosopher Bertrand Russell argued that sexual compatibility is essential to a successful marriage and should be tested beforehand—just as one would inspect a house before purchase.

“It seems absurd to ask people to enter upon a relationship intended to be lifelong, without any previous knowledge as to their sexual compatibility.”
– Bertrand Russell, Marriage and Morals

Žižek: Sex as a Spiritual Act

Philosopher Slavoj Žižek challenges the Catholic view that non-reproductive sex is “animalistic.” In fact, he argues the opposite:

“Sex spiritualizes itself only when it abstracts from its natural end and becomes an end-in-itself.”
– Slavoj Žižek, Disparities

In other words, only humans turn sex into something existential and transcendent—a break from daily life and a pathway to another dimension of experience. It is precisely because humans do not treat sex merely as a reproductive act that it becomes metaphysical.

A Final Analogy

Sex, as a natural faculty, could be likened to a Swiss army knife. A specific function may be activated at any given time—cutting bread, opening a bottle, magnifying something—but it is absurd to insist that only one function defines the tool’s true purpose. Reproduction may be one valid purpose of sexuality, but it is not necessarily the only or indispensable one.

As Robin Gill aptly summarizes:

“Even if it is conceded that procreation is the obvious function of sexuality, it is far from clear that it should be the only, or the indispensable, function of human sexuality.”
– Robin Gill, A Textbook of Christian Ethics

The Contextual Nature of Sexual Purposes

Each possible natural ultimate purpose of sexuality—personal maturity, emotional union (love), and health promotion—arises in its own distinct context: adolescence, emotional bonding, and bodily well-being, respectively. As previously argued, once one of these purposes is actively pursued and fulfilled, the others recede in moral and practical relevance within that specific context. They may still occur incidentally, but they are not morally significant in that moment.

The Exclusivity of Primary Purpose

Logically, any action can have only one final cause at a time within a given context. The principle of non-contradiction prevents us from attributing multiple simultaneous primary ends to a single, coherent process. This can be illustrated metaphorically:

Imagine a cube, with one face representing sexual activity. Each possible primary purpose is symbolized by a color. If reproduction is green, then all means to that end must also be green. Mixing in red (e.g. emotional bonding) would dilute the unity of purpose. If another end is pursued—say, love, represented by red—then the entire face must be red, including all corresponding means (e.g. foreplay, even contraception). Mixing colors (i.e. purposes) fragments intention and undermines teleological clarity.

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1. Personal Maturity as a Sexual Purpose

Sexuality plays a fundamental role in psychosexual development, especially during adolescence, long before reproduction or marriage are realistic goals. Responsible family life requires emotional and psychological maturity, which often necessitates a developmental phase of sexual exploration and experience.

Experts—including those cited by Catholic thinkers like Edward Feser—acknowledge that psychosexual development is inseparable from cognitive and emotional growth, beginning in infancy and evolving through adolescence. During puberty, boys experience involuntary ejaculations (e.g. nocturnal emissions) and sexual curiosity arises in peer interactions. These phenomena, while biologically mature, do not imply readiness for reproduction or moral commitment to procreation.

Thomists may agree that personal maturity is a prerequisite for marriage, yet it is inconsistent to suggest that all adolescent sexual activity—e.g. two 13-year-olds kissing or experimenting—must already be morally tied to reproduction. Such acts are better understood as part of a coming-of-age process, not as violations of natural law.

Even if this maturing process involves “non-procreative” acts, they can still serve a legitimate natural end—the gradual cultivation of personal readiness for future relational and sexual commitments.

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2. Love and Emotional Union

Human beings are not merely biological or reproductive creatures; they are also spiritual, emotional, and erotic. The unitive function of sexuality—emotional and spiritual bonding—can exist independently of procreation and is often seen as an equally important natural purpose.

Christians often cite Matthew 19:5–6 (“the two shall become one flesh”) as affirmation of this relational dimension. However, if love is considered only a secondary or optional feature of sexual ethics, absurd consequences follow: Are married couples morally obligated to reproduce even if they no longer love each other? Should love be dismissed as morally irrelevant unless it facilitates procreation?

If love is merely a means to reproduction, it becomes logically dispensable. But this is clearly not the Catholic understanding. Therefore, love must be acknowledged as an end in itself—a primary natural purpose of sexual activity.

Moreover, contraceptive sex in a loving relationship may preserve that unitive purpose, especially when pregnancy would hinder it (e.g. due to health or economic hardship). Indeed, as Germain Grisez argues, contraception may support morally legitimate ends that are not themselves procreative.

“Contraceptive intercourse can have the same good purposes as other licit though unfruitful sexual relations.”
— Germain Grisez, Contraception and the New Natural Law

Redefining the "Unitive"

Theologian Jim Vaughan has rightly questioned traditional definitions of “unitive sex” as strictly involving semen deposition in the cervix:

“Why is the male gamete but not the female gamete relevant? […] I would redefine the unitive moment as a mental/spiritual one—e.g. the moment of orgasm. The use of condoms therefore ceases to be ‘evil’ or even relevant.”
— Comment on Philosophy Bites

If humans can express love through non-vaginal sex—such as oral sex—then these forms, too, may serve the unitive purpose.

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3. Health as a Natural End

Sexual activity has well-documented health benefits: it strengthens the immune system, alleviates stress and depression, and promotes overall well-being. These are not incidental effects but can be viewed as part of sex's teleological function—especially in post-reproductive or non-reproductive contexts.

Aristotle acknowledged this in Politics:

“Couples where the man is over 54 should cease from having families and from that time forward cohabit only for the sake of health.”
— Politics, Book VII, Part XVI

This suggests that in certain life stages, health becomes a legitimate and primary natural end of sexual activity.

Even in Thomistic ethics, the preservation of life and health ranks among the highest goods. Just as amputating a limb to save one’s life does not violate natural law, so too sexual activity for health reasons can be morally justified—even if it temporarily frustrates the reproductive function.

Urologists and health professionals, for instance, recommend regular sexual activity or masturbation to maintain genital health. These expert recommendations, if taken seriously by Thomists like Feser (who appeal to natural science), ought to be morally permissible.

The Treadmill Analogy

A friend once suggested that using a treadmill frustrates the natural purpose of walking—i.e. to move from A to B. Yet no one objects to treadmill use for health reasons. The act of walking remains the same; only the purpose shifts. Likewise, sexual activity that doesn't pursue reproduction isn't necessarily immoral if its end is physical or emotional well-being.

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On the "Perverted Faculty" and Purpose Misuse

According to Thomistic natural law, there is a crucial distinction between:

• “Other than” uses of a faculty (morally neutral)
• “Contrary to” uses (morally wrong)

Feser uses this distinction to defend natural law against common counterarguments:

“Critics object that using organs for other than their biological purpose—like feet for kicking a football—is morally unproblematic. So why is non-reproductive sex wrong?”
— Harry Gensler, Ethics: A Contemporary Introduction

The problem is that this defense often appears ad hoc. For example, if the foot has multiple legitimate uses—walking, dancing, pedaling, even drawing—why can’t sexual organs have more than one natural purpose? The arbitrariness in assigning moral significance to some faculties (e.g. genitals) but not others (e.g. hands or feet) is logically untenable.

Chris Meyers makes this point forcefully:

“If it is not morally wrong to use a foot for something other than its purpose, then the same should be true of the genitals. To claim otherwise is ad hoc, proposed only to defend a preexisting conclusion.”
— Chris Meyers, The Moral Defense of Homosexuality

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Concluding Reflection

Even if one does not accept the three non-procreative ends of sexuality (maturity, love, health) as naturally primary, they can still be seen as morally neutral "other than" uses—not "contrary to" uses. Thomism hinges on the validity of that distinction. But if the line between “other than” and “contrary to” cannot be coherently drawn, the entire framework collapses.

As the opening question on this Philosophy StackExchange thread insightfully asks:

Is the Perverted Faculty Argument sound?

Without a consistent way to define what counts as a morally impermissible use of a natural faculty, the teleological ethics of Thomism becomes vulnerable—not just to isolated counterexamples, but to a collapse in its internal logic.

Rethinking Purpose and Misuse in Natural Law: The Case of Sexuality

1. Purpose, Misuse, and the Walking Analogy

According to Thomistic natural law theory, bodily faculties have natural purposes which must not be deliberately frustrated. Take, for example, the ability to walk. Its natural purpose is arguably to enable movement from one location to another (from point A to point B), and secondarily, to support self-preservation.

Yet there are clear cases of "misappropriation":

1.     Treadmill use – Walking occurs, but one remains in place. The purpose of locomotion is not fulfilled.

2.     Soccer – Legs and feet are used to kick a ball, which deviates from walking’s natural goal.

In both examples, natural functions are used in ways that do not directly promote self-preservation, nor do they contribute to the procurement of necessities (like food) or reproduction. If these uses are not morally blameworthy, the implication is clear: not every deviation from a biological function constitutes a moral failure.

The issue, then, is one of hierarchical goods. Is self-preservation a higher good than reproduction? If so, then sexual activity which promotes emotional or physical well-being—even without procreative intent—could be morally justified.

One might argue that reproduction is merely a function of self-preservation, applied at the species level. But once this is granted, disputes over the hierarchy of ends and their moral weight become inevitable.

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2. Is Reproduction the Sole Natural Purpose of Sex?

The principle that “every potentially fertile sexual act must serve reproduction as its primary end” is often treated by natural law theorists as axiomatic. But this is misleading. It is not a self-evident principle, but rather a conclusion drawn from metaphysical and theological premises, many of which are historically and scientifically questionable.

Consider Edward Feser’s summary in The Last Superstition, where he argues that the misuse of sexual faculties is serious because sex concerns “the preservation of the species” and the welfare of men, women, and children. He follows Aquinas in claiming that the deliberate frustration of the reproductive purpose is intrinsically immoral, with no exceptions:

"The inordinate emission of semen is incompatible with the natural good; namely, the preservation of the species."
— Summa Contra Gentiles, III.122

But this reasoning borders on circularity. The logic can be summarized as:

• Q: Why must I not undermine procreation during sex?
  A: Because procreation is important.
• Q: Why is procreation important?
  A: Because sex is ordered toward procreation.
• Q: Why is frustrating the function of sex wrong?
  A: Because sex’s function is the preservation of the species.
• Q: Why is preservation of the species important?
  A: Because that’s the function of sex.

This line of argument doesn’t justify the central claim—it merely reasserts it in different terms.

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3. Atomizing Human Faculties: The Problem of Isolated Functions

Natural law thinkers like Feser and Aquinas treat reproductive capacity as an independent moral good—almost as if it has “absolute rights of its own” (Grisez). But this raises a problem: it fails to consider the human person as a whole.

As Peter Vardy notes:

"To separate genitalia out as having a particular purpose on their own without considering the whole complexity of a person’s relationship to his or her body, psychology, sexuality […] may be a diminution of human beings as people."
— The Puzzle of Ethics

We are not a collection of isolated biological functions. Moral reasoning must take into account the psychophysical unity of the human being. To reduce sexuality to a procreative mechanism is to disregard its rich roles in love, emotional bonding, personal development, and even health.

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4. Aquinas, Misuse, and the Case of Cotton Swabs

Aquinas offers examples of “harmless” misuses of faculties: walking on hands, or using feet as substitutes for hands. Feser, in The Last Superstition, extends this logic to ear-cleaning with cotton swabs. The ear, he explains, cleans itself naturally by pushing wax outward. Cotton swabs reverse this process, frustrating the ear’s natural function.

But this example undermines Feser’s own framework:

• Ear cleaning is teleologically counter to the natural self-cleaning process.
• Medical experts warn it can cause injury, infection, or even hearing loss.
• Feser dismisses this as a minor lapse—a small “sin against prudence.”

By that logic, if frustrating a natural process with possible serious consequences is only a minor offense, then why is a non-procreative sexual act—without harmful consequences—a grave offense?

In reality, such “frustrations” of nature are often justified by higher goods: hygiene, health, comfort, or social utility. Cotton swabs, even if imperfect, are used to assist natural processes, not necessarily oppose them. Intent matters. Most people do not intend to “violate” nature by using them.

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5. The Historical Weight of Reproduction: Two Premises

Natural law’s heavy moralization of reproduction is arguably built not on logic, but on historical and emotional premises:

1.     The preservation of the species is an overriding good.
Reproductive sex is sacralized by linking it to the survival of humanity. But this often leads to an equivocation between the act of sex and the continuation of the species—suggesting sophistry more than sound ethics.

2.     Male semen contains the complete, preformed human being.
Inspired by Aristotle and older biological theories, Aquinas and early Thomists held that the male provides the form and the movement impulse for life. This gave semen an almost sacred status, leading Aquinas to call non-reproductive emission a crime “second only to homicide.”

As Anthony Kenny notes:

"Such a view was natural in the context of a biological belief that the sperm is an early stage of the very same individual as eventually comes to birth."
— Medieval Philosophy

These outdated beliefs no longer hold in modern biology. Sperm is not a preformed human being, and reproduction is a joint contribution of male and female gametes.

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6. Moral Weight and the Collapse of Distinctions

If we drop both of the above premises, the moral weight placed on procreative sex becomes difficult to sustain. In fact, preventing reproduction may be as morally trivial as walking on one’s hands or cleaning one’s ears.

If only Premise 1 (preservation of the species) is maintained, it still does not logically follow that every potentially fertile sexual act must be directed toward procreation. Other important goods—such as personal maturity, physical health, or even environmental factors like overpopulation—may justify limiting or avoiding reproduction.

As Aristotle himself acknowledged, too-early or too-late reproduction harms the child and should be avoided:

"[Couples] should cohabit only for the sake of health."
— Politics, Book VII, Part XVI

Thus, a rigid procreative imperative ignores important ethical considerations, including those central to responsible parenthood, health, and human development.

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7. Conclusion: A Call for Holistic Ethical Reasoning

Aquinas and modern Thomists tend to isolate the sexual faculty and treat reproduction as an inviolable moral absolute. But the examples of walking, ear cleaning, and soccer show that natural functions can be repurposed, even “frustrated,” without necessarily being morally wrong.

If intent, context, and higher goods matter in the use of most bodily faculties, why are they dismissed in the case of sexuality?

A genuinely holistic natural law theory must acknowledge the complexity of human nature—not merely its biology, but its emotional, psychological, social, and spiritual dimensions. Without this, the moral weight given to procreative sex rests not on reason, but on a long-outdated metaphysical legacy.

The Principle of Totality and Human Sexuality: A Critical Examination

1. Man as a Political and Social Being

According to Aristotle, man is by nature a political and social being—he needs the polis or the state. This fundamental nature implies that human flourishing is realized within a communal and structured context. If this is so, might it not follow that the requirements of the state define the final cause of human actions and thus inform the interpretation of the principle of totality? Aristotle seems to suggest this by establishing the polis as a moral standard. Hegel radicalized this idea by pushing the primacy of the state to its extreme.

2. The Reproductive Imperative and Its Limits

It is generally assumed that all humans are expected to reproduce eventually. Yet, this expectation presupposes that reproduction must occur under conditions beneficial to the survival of humanity. Based on this, certain behaviors might be condemned: self-castration, voluntary childlessness in stable marriages, gay marriage, and priestly vows of celibacy—acts that are perceived to oppose human propagation.

However, this premise is deeply problematic. Antinatalism offers strong counterarguments, citing the cruelty of the world, political instability, and bleak future prospects. More critically, the moral necessity of preserving humanity remains unproven. It cannot merely be asserted, especially not on theological grounds, nor can circular reasoning be tolerated. Preservation of the species is a neutral, amoral matter. Some support it; others oppose it; many remain indifferent. Our moral obligations pertain only to those who already exist.

3. Religious Overtones and the Preservation of Humanity

Traditional religious views, particularly within Catholicism and ancient Judaism, have historically reinforced the obligation to reproduce. Rabbi Eleazar ben Azariah likened refusal to marry and procreate to murder. Rabbi Eliezer echoed this sentiment. The idea that not reproducing is tantamount to killing reveals a deep theological and cultural commitment to population growth.

Yet these commands derive from specific historical and cultural conditions. They cannot claim universal validity without scrutiny.

4. Reframing the Principle of Totality

One might compare two forms of preservation: the continuation of the species versus the preservation of one's hearing, a sense intimately linked to reason. Personally, I prioritize the latter. From this standpoint, using cotton swabs (despite the risk to ear health) would be more morally significant than practicing coitus interruptus, which, while contraceptive, still allows for the release of sperm.

If I accepted natural law theory, I would still argue that contraceptive sex could serve the overall good of the individual. The principle of totality permits removal of diseased reproductive organs for the health of the body. Why, then, is contraception forbidden if it similarly promotes individual well-being?

5. Contraceptive Sex and the Common Good

Why should contraceptive intercourse not be seen as serving the good of the whole person, especially if it alleviates psychological distress? If I conclude that pregnancy would be harmful to my well-being, then contraceptive sex serves my overall good. The principle of totality should not be interpreted rigidly or solely in religious terms. It could instead support a broader vision of the good life, rather than a survival-oriented asceticism.

Natural law thinkers allow for exceptions in other domains. For instance, the use of cow’s milk—intended for calves—is widespread, despite its being "contrary to nature." Similarly, using books as firewood or as props, or smashing dishes in rituals, are all accepted. Why should human sexuality be uniquely exempt from such pragmatic flexibility?

As Alan Donagan has asked: if we may manipulate sub-rational natural things for our own purposes, why should it be inherently wrong to do so with our own natural functions?

6. Reproduction and Technological Mediation

Even within Thomistic thought, artificial intervention is not always wrong. Masturbation to obtain semen for fertility testing, for example, serves a reproductive purpose. Artificial insemination can be justified under certain conditions. If we accept medical aids like glasses to correct sight, why not accept artificial methods to assist conception?

Ironically, the Church allows semen collection via a perforated condom to preserve the “form” of the act, even when natural conception is impossible. Here, the symbolic form outweighs the goal of procreation. This illustrates a preference for form over function, revealing a deeper superstition rooted in preserving a supposed "natural order."

7. Sexuality and the Conservative Project

Sexuality remains the final stronghold of cultural conservatism. Conservatives cling to rigid sexual ethics in an effort to resist liberal cultural transformation. Natural law often functions as a vehicle for this ideological battle.

Superstition often underpins these natural law arguments—a fear of disrupting a fragile cosmic or moral order. This fear is reminiscent of ancient animist beliefs, where improper conduct was thought to offend gods or spirits. Today, the “order” of natural functions is treated with similar reverence, often at the expense of human intention or well-being.

8. Biological Underpinnings of Sexual Morality

Modern evolutionary psychology suggests that sexual ethics may be less about theology and more about reproductive strategy. As Douglas Kenrick and Robert Kurzban argue, people support moral systems that align with their reproductive interests. For example, lower-status males benefit from monogamy and thus are more likely to support strict sexual norms.

Thus, sexual moralism may stem from evolved strategies rather than divine mandates. This also explains why sexuality, more than any other domain, becomes a battleground for moral norms.

9. Lactation as Analogy: The Grisez Example

Germain Grisez offers a revealing analogy. Lactation, like sex, involves a biological process with a natural end—yet mothers are permitted to pump and discard breast milk during temporary separations from their child. No serious moral issue is raised. If this is permitted, why is contraception—another case of interrupting a natural function—condemned?

Clearly, the rejection of contraception cannot rest on the mere frustration of a natural faculty.

10. Conclusion: Reclaiming the Role of Intention

Ultimately, the moral worth of an act lies in the intention behind it, not in its outward conformity to a supposed natural order. As Paul J. Weithman puts it, it is difficult to see how the biological facts of reproduction carry decisive moral weight. To think they do is to mistake physical form for moral substance.

In Schopenhauer’s words:

“The intention alone decides on the worth or unworth of the deed, which is why the same deed, according to its intention, can be reprehensible or praiseworthy.”

III.1) Scattered Remarks and Additions – Sometimes More, Sometimes Less Convincing

The Problem of Aristotelian Teleology

Thomistic natural law ethics rests heavily on Aristotle’s doctrine of final causes—that all natural things act toward ends. However, this metaphysical framework is beset with deep problems:

1.     Historical and Scientific Anachronism
Aristotle’s teleological metaphysics stems from an outdated biological model of the world. Once science moved toward Newtonian mechanism, and later quantum indeterminism, Aristotelian teleology became obsolete. Reintroducing it amounts to metaphysical sleight-of-hand, resembling theological projection rather than a viable scientific explanation (Capaldi, Using Natural Law to Guide Public Morality).

2.     Epistemological Obscurity
We can neither empirically observe nor logically deduce the ultimate purpose of a thing. Any teleological claim remains hypothetical. For example, an organism might exist for reproduction, power expansion, death, ecosystem balance, or even as food—without clear priority among these.

3.     Hierarchy of Purposes and Circularity
Ackrill questions whether it’s coherent to attribute a purpose to the whole animal, much less the species. If a dog’s purpose is to preserve the species, what is the species for? Aristotle answers: for perpetuation. But this becomes a circular explanation with no terminus (Ackrill, Aristotle the Philosopher).

4.     From Function to Value
Even when functionality is clear (e.g., an elephant’s trunk), purpose at the level of the whole remains speculative. The claim that natural organisms act for "the best" imports unexamined optimism (Mauthner) and anthropocentric valuation—i.e., nature works not just toward ends, but toward good ends. But how do we know what is “best” for a piece of iron—or the universe?

Internal Contradictions in Final Causality

Aristotle’s concept of locus naturalis (natural place) posits that iron, when thrown, falls because it “seeks” to return to Earth. This ascribes purpose to gravity. But modern science no longer accepts this. Teleological explanations have been discredited like phlogiston or the ether—concepts now seen as pseudo-explanatory relics.

Moreover, teleology often masks complexity. The moon’s orbit, for instance, is not an effect of a single aim but a resultant of multiple forces. To say that it orbits “in order to orbit” is a tautology. Most natural processes are resultant motions, not goal-directed ones.

Critiques from Philosophy and Science

• Kant relegates final causes to a regulative idea—useful heuristically, but illegitimate ontologically.
• Mauthner calls teleology a linguistic illusion: Aristotle assumes design where none is evident.
• Lewes ties teleology to anthropomorphic thinking—like seeing gods in thunder.
• Nietzsche rejects the world-as-organism metaphor entirely. The universe, he says, is not purposeful but chaotic, devoid of human values, laws, or aims (The Gay Science).
• Beiser points to the metaphysical absurdity: How can a future, idealized end act on the present?
• Anthony Kenny ridicules Aquinas’ claim that water freezes because it “aims” to freeze: this is empty repetition.

The Collapse of Teleology into Ethics

The Thomist idea that efficient causes imply final causes, and that final causes imply value, creates a problematic moral conclusion: that everything natural is good, and everything that occurs does so for the best. This view cannot accommodate errors, defects, or evil—they all become part of a teleological whole. Hence, natural law risks becoming ethically vacuous.

Furthermore, if all efficient causes are also final causes, then natural law becomes unfalsifiable. Every event—even suffering—must be “for the best.” But this undermines ethical deliberation altogether.

The Dangers of Value-Loaded Natural Law

Natural law depends on three controversial steps:

1.     Asserting a natural purpose

2.     Attaching value to that purpose

3.     Deriving moral obligations from the value

Each step is fraught with problems:

• Purposes are speculative.
• Values are comparative and subjective (Schopenhauer).
• The leap from value to moral obligation commits the naturalistic fallacy (Nielsen).

Schopenhauer rightly emphasized that value is always relative and observer-dependent. Aristotle, by contrast, smuggles in patriarchal, anthropocentric, and culturally contingent standards—e.g., male over female, above over below, free man over slave. These value hierarchies are not rationally justified but reflect the prejudices of his time.

Values and Subjectivity

All values are imposed by subjects. Aristotle’s notion of “the good” in nature stems from the assumption that what is functional is also good. But this is questionable. A deformed squirrel may be less “essentially instantiated,” yet that doesn't make it bad.

Nietzsche warns against treating contemporary man as the eternal standard. There are no eternal values—only historically and psychologically contingent ones.

Even Aristotle himself admits that human good consists in the good performance of human functions—i.e., a normative layer is added to the natural function (Gewirth).

Natural Law as Ideological Smokescreen

As L.A. Rollins argues, “natural law” often serves to disguise personal preferences as objective truths. Wilhelmsen’s claim that pornography is objectively bad is, in fact, a subjective moral stance disguised as natural necessity. Such rhetorical strategies are ideological tools.

As Kai Nielsen concludes, even if final causes exist, they don’t generate moral norms. Any derivation of "ought" from "is" involves hidden premises that are themselves moral in nature.

Ultimately, morality and law must be freed from the illusion of natural objectivity. Otherwise, they become tools for imposing ideology under the guise of metaphysics.

A Convincing Alternative: Conscious Freedom and Moral Obligation

T. M. Murray presents a compelling starting point for an alternative ethical theory. He writes:

"It seems that what is distinctive of human nature, or what is universal to all of us in distinction from animals, is not our particular biological capacities, but conscious freedom to direct our lives within the limits set for us. Conscious freedom, or the ability to act for reasons of our own making, appears to be the most common basis of our human nature."
(Murray, T. M., Thinking Straight About Being Gay)

This view resonates with the Enlightenment's shift toward secular ethics, notably beginning with Immanuel Kant. Prior to Kant, one could argue there was no fully developed, objective, and secular ethical system. Kant's famous maxim that we must treat humanity "never merely as a means, but always at the same time as an end" was groundbreaking. However, as Gerold Prauss points out in Moral und Recht im Staat nach Kant und Hegel, Kant does not sufficiently explain why people are ends in themselves.

Prauss suggests a significant philosophical innovation: shifting focus from the actor’s moral intention (as Kant does) to the perspective of the one being acted upon. Morality, he argues, is not solipsistic—it is inherently interpersonal.

As previously noted, the concept of “ought” implies a will external to one’s own. According to Prauss, we can relate to others in three morally significant ways:

1.     Merely as means, which characterizes evil (e.g., harming, lying, killing, or ignoring someone in need);

2.     As both means and ends, which typifies ordinary social interaction (e.g., taking a taxi, entering a contract, engaging in consensual sex);

3.     Only as ends, applicable especially to those unable to help themselves—such as an injured person needing aid.

In the latter case, the person's status as a self-conscious, free creator of ends imposes a non-optional moral claim on any bystander. This claim need not be spoken; its potentiality suffices. Failing to respond is not just morally neutral—it is an act of evil. A person in need becomes, by virtue of their status as a conscious end, a morally binding obligation for others. Ends in themselves are logically binding on any rational will.

Thus, for Prauss, ethics is rooted in:

• Self-recognition (seeing oneself as an end), and
• Interpersonal recognition (acknowledging others as ends).

In his words:

“Each human is a conscious will or end in themselves. And because everyone knows this of themselves and others, each becomes a conscious demand upon all others, creating a binding obligation. Everyone wants to be treated at least as an end, and sometimes only as an end—particularly when incapable of self-help.”

In short, rational agents constantly issue imperatives, but only in certain interpersonal contexts do these imperatives result in objectively binding moral duties.

To close this section, a quote by Richard Robinson captures the essence of this shift:

“Once we have explicitly asked ourselves why we should do anything just because nature does it, or why we should aid nature in her purposes, we see that there is no reason why we should. Let nature look to her own purposes, if she has any. We will look to ours.”
(Quoted in Donagan, A., in: Aquinas – A Collection of Critical Essays, ed. Anthony Kenny, 1969)

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The Problem of Natural Law and Shaving

Thomistic natural law argues that biological functions have purposes, and interfering with them is immoral. But if we take this seriously, shaving becomes morally problematic.

Hair has clear biological functions—eyelashes and eyebrows protect the eyes; axillary and pubic hair serve both protective and signaling purposes. Aristotle noted the protective role of human head hair due to the brain's need for thermal regulation (Parts of Animals II.14).

Thus, by shaving, especially areas like the pubic region, one arguably interrupts natural functions—a violation of natural law. Even if minor, such an act still constitutes a perversion of function. Schopenhauer, ironically both defender and critic of the beard, argued it concealed emotional expression—yet also recommended shaving to emphasize humanity over masculinity.

The satirical conclusion is sharp: If pubic hair protects against infection and friction, as even modern health sources argue, then shaving it, particularly for aesthetic reasons, becomes an unnatural and potentially immoral act. And if this moral logic is taken seriously, the risk of shaving becomes spiritually hazardous.

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The Problem of Anesthesia: A Thought Experiment

Let us entertain an intuitionist defense of natural moral absolutes: Is anesthesia immoral?

One could argue, analogously to Anscombe’s rejection of contraception, that while natural cycles of consciousness exist (like sleep), artificially inducing unconsciousness (as in surgery) perverts nature’s intent. Although sleep is natural, choosing to disconnect reason and sensation is not.

Even though painkillers can alleviate suffering, they also tempt abuse. Without absolute prohibitions, how do we morally distinguish between anesthesia during surgery and drug-induced unconsciousness during grief—or even for fun?

Peter Geach (in The Virtues) addressed this issue:

“If it were a duty to be mentally as much alert as possible for as long as possible, this might speak against any consumption of alcohol at all. But of course there is no such duty. … Aquinas has remarked that it is a precept of reason that the exercise of reason should be intermitted... there is nothing immoral in taking sleeping-pills or having a doctor give you anaesthetics for an operation.”

But why is the intermittency of fertility not a normative justification for contraception, while the intermittency of consciousness justifies anesthesia? The analogy undermines the consistency of natural law methodology.
(cf. James M. DuBois, “Is Anesthesia Intrinsically Wrong?”, Christian Bioethics, 2008)

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Alcohol and Natural Law

Drinking alcohol for amusement may also conflict with natural law. Voluntarily ingesting a toxin that dulls rationality and promotes irrational or aggressive behavior seems inconsistent with human dignity and rational nature.

Some Thomists might appeal to alcohol’s role in sociability. But this “sociability” often devolves into hedonistic indulgence, empty rhetoric, or even misconduct. From a natural law perspective, willingly impairing one’s rational faculty is gravely problematic—yet culturally normalized, even among devout Catholics.

And yet, might moderate intoxication serve a restorative function? Could an occasional “mental reset” provide emotional balance in a stressful life? This pragmatic argument resists absolute moral condemnation—though traditional Thomists are unlikely to accept it.

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Chewing Gum and Condoms: A Satirical Analogy

Consider the following satirical parallel:

• Chewing gum activates the eating function but deliberately avoids its telos (digestion).
• Using condoms activates the reproductive function but deliberately avoids its telos (procreation).

In both cases, a natural faculty is used for pleasure while frustrating its natural end. If natural law condemns the latter, should it not condemn the former?

Chewing gum stimulates saliva and mastication, misleading the digestive system without fulfillment. Likewise, condoms allow sexual pleasure but block reproductive fulfillment. Therefore, chewing gum becomes a moral absurdity under strict natural law logic—yet society accepts it casually.

This reductio ad absurdum exposes the rigidity of certain natural law arguments.

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Milk, Sperm, and Functional Fluids

A breastfeeding woman can extract milk for fun; a man can ejaculate for fun. Both acts involve manual stimulation of functional biological fluids without their designated recipient (infant or female partner). If natural law condemns one (e.g., masturbation), it must also condemn the other (e.g., milk expression for amusement).

But this would be bizarre. Thus, such logic reveals the incoherence or arbitrariness of applying natural law selectively.

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Conclusion

Natural law theory often relies on teleological assumptions about biological functions. Yet when pushed consistently, it leads to absurd or untenable conclusions—condemning everything from shaving and chewing gum to anesthesia and breastfeeding for fun.

If we accept the notion that conscious freedom, interpersonal recognition, and rational self-awareness are the true foundations of ethics—as thinkers like Murray and Prauss suggest—then ethical obligations arise not from biology, but from our shared status as free agents and ends in ourselves.

The Problem of Moral Incentives

1. What Really Motivates Moral Action?

What are the actual motivating forces that drive us to act in accordance with natural law? This question is far from trivial, since no moral good can be achieved without an impulse to pursue it. Edward Feser, for example, mentions disgust as a possible motivator. But disgust is a questionable moral force, as history shows. It has played a decisive role in discrimination against interracial marriage, where the feeling of disgust served as justification. Moreover, what one generation finds disgusting, another may find appealing. Disgust alone, then, cannot serve as a reliable moral compass.

For Schopenhauer, by contrast, there is only one true moral driving force: compassion. In this, he aligns with Buddhism and even Christianity. He writes:

“Nothing outrages our moral feeling in its deepest ground so much as cruelty... The sense of that question ['How is it possible to do such a thing?'] is quite certainly simply this: How is it possible to be so much without compassion? ... Consequently, compassion is the real moral incentive.”
(Arthur Schopenhauer – The Two Fundamental Problems of Ethics)

This raises a serious question: what if an act stems from compassion but violates so-called natural law? Is such an act immoral simply because it doesn’t conform to a predetermined structure?

2. The Limits of the Term "Good"

Peter Geach highlights another problem. He notes that calling something a "good A" has no motivational power unless the person already wants an A. The term “good” alone doesn’t compel action. Saying "you have ants in your pants" is more likely to spur action than saying "this is a good way to live."

This point is developed further by Shalina Stilley:

“Just as calling a can of sardines ‘good’ won't make someone eat it unless they want sardines, calling certain traits ‘good’ or ‘essential to the human person’ won’t move people unless they already desire those traits.”
(Shalina Stilley, Natural Law Theory and the 'Is-Ought' Problem)

Thomists, however, often collapse "good" and "ought" into each other, which is deeply problematic. Just because something is "good" does not mean that everyone ought to pursue it. Locke understood this long before Kant:

“It would be utterly in vain to suppose a rule set to the free actions of man, without annexing to it some enforcement of good and evil to determine his will.”
(John Locke, An Essay Concerning Human Understanding)

So, the “ought” is inherently tied to consequences—punishment or reward—and is therefore hypothetical, not categorical. If God’s judgment is the sole enforcer of morality, then morality becomes transactional. As Schopenhauer notes:

“Support through divine reward or punishment turns every unselfish action into selfish calculation.”
(Schopenhauer, Parerga and Paralipomena)

3. A Nietzschean Challenge

If I understand myself as a teleological whole, then my conscious will expresses this whole. My individual parts exist only in service of this will. To discover my true will, I must free myself from all conventions and imposed standards. Why compare myself to others? The task is to find myself—not to conform. If someone insists that their priestly nature is normative for all, I will simply wrinkle my nose.

4. The Unfathomable Thomists

Thomists often speak with great confidence about human organs and faculties. One would expect, then, that they could present a complete chart of these faculties and their respective functions—especially to support claims like Feser’s about proper and improper uses (via his "contrary to" and "other than" distinctions).

When a Thomist claims sexuality has only one main purpose—procreation—we must ask: how does he know this, and what exactly does he mean by "sexuality"? If his knowledge is intuitive, others can intuit differently. If it’s empirical, what data does he rely on? Anatomy and reproduction alone are insufficient, especially when species like bonobos use sex for a range of social functions. A full biological understanding must include behavioral patterns, psychological dispositions, and perhaps even genetics.

Sexuality is not reducible to reproduction. Flirting, love, eroticism, touch, voice, and countless subtle elements are part of human sexual experience. To say that any partial activation of this complex must aim at reproduction is absurd.

5. The Circularity of Natural Law Reasoning

Much of the natural law reasoning is circular:

• What are the right inclinations? Look at anatomy and physiology.
• Why trust anatomy and physiology as moral indicators? Because they correspond to our inward inclinations.
• Why trust those inward inclinations? Because they reflect natural law.

This circular reasoning reveals itself when Thomists call critiques "straw men"—yet often, only a slight shift in interpretation turns their straw men into steel men. Their conceptual distinctions are fragile and often seem tailor-made to defend traditional sexual norms rather than reasoned ethical conclusions.

6. The Limits of Teleology

You can claim every organ, down to cellular parts, serves a purpose. But functions are nested in hierarchies. Chewing serves digestion, digestion serves self-preservation, and so on. But this hierarchy is flexible. I can "pervert" chewing (e.g., by grinding my teeth) while still fulfilling muscular or neurological functions. The same flexibility must apply to sexuality. Saying the procreative faculty must always serve reproduction is as trivial—and flawed—as saying the eye must always be used to see beauty, never ugliness.

Teleological analogies collapse under complexity. If the Thomist claims sexual and generative faculties are uniquely teleological and incomparable to any others, we are no longer reasoning—we are dogmatizing.

7. The Problem of Enforcement and Social Application

A coherent natural law theory would require a clear moral hierarchy: Is murder worse than theft? Is sodomy worse than adultery? Should adultery again be a crime? Should suicide attempts be punished? Should masturbation incur the death penalty?

When the Church (or any authority) attempts to legislate natural law, revolt becomes a moral obligation. Worse still, natural law can’t even tell us what social system best fits it. Perhaps communism fits better than capitalism? Plato certainly thought so.

8. The Thomist’s Moral Dilemma

According to Thomistic ethics, a man shouldn’t leave his child, especially after fathering it. Yet if he wishes to lead a “holy life,” he can abandon wife and child with impunity. Suddenly, the child’s wellbeing matters less than personal sanctity. If holiness is the highest end of human nature, it cannot be optional. Why then should Christians marry at all?

Jesus urged radical detachment from family:

“The Jesus of history was not a proponent of 'family values'. He urged his followers to abandon home and family for the coming Kingdom.”
(Bart Ehrman, Jesus: Apocalyptic Prophet of the New Millennium)

Historically, Catholicism has seen virginity as superior to marriage:

“Perpetual chastity appears in itself as the highest merit of man... This belief is deep-rooted in Christianity.”
(Der Katholik, 1831, quoted by Schopenhauer)

This leads to a schizophrenic position: Old Testament natalism versus New Testament anti-natalism.

Nietzsche sums it up brutally:

“If Christian dogma were true, then to live as an ordinary Christian would be sheer idiocy. One ought to become a monk, a saint, a fanatic—anything but a worldly man.”
(Nietzsche, Human, All Too Human)

9. Thomistic Consequentialism?

Despite appearances, much of Aquinas's ethics relies on consequentialist reasoning. He believed sexual pleasure had no intrinsic value and justified marriage solely for procreation and child-rearing. His insistence on monogamy, his rejection of polygamy, and even his valuation of celibacy rest on what he saw as the best societal outcomes, not revelation.

As Bamforth and Richards note:

“Thomas clearly reasoned in a consequentialist fashion... His methodology demands that arguments be grounded in the best available science and philosophy of the day.”
(Bamforth & Richards, Patriarchal Religion, Sexuality, and Gender)

Viewed from a modern perspective, many of Aquinas’s conclusions—especially regarding gender and sexuality—are outdated and even embarrassing.

10. A Final Curiosity

Bertrand Russell notes a bizarre argument from Aquinas against sibling incest:

“If the love of husband and wife were combined with that of brother and sister, the mutual attraction would be so strong as to cause unduly frequent intercourse.”
(Russell, History of Western Philosophy)

What Exactly Is Sex? A Philosophical Challenge to Natural Law

1. The Unclear Foundations of Thomist Sexual Ethics

Thomists speak confidently about when sex becomes morally wrong—without clearly defining what sex is. That is presumptuous. One cannot assume a Platonic ideal of “sex” without offering a precise definition.

Take a basic case: I fall deeply in love and experience strong romantic and sexual desire. If I suppress this for superstitious or external reasons, is this suppression morally sound under natural law? Does the mere experience of love or arousal mark an irreversible point in the sexual teleology leading to marriage, as Catholicism sometimes suggests?

If so, where is that point of no return? Is it during flirting? A kiss? A caress? Orgasm without ejaculation? Natural law requires a clear teleological structure, yet it cannot determine this point precisely. The whole system begins to unravel under scrutiny.

2. The Problem with Feser's Sexual Framework

Feser claims that sex begins with arousal (a subjective inner state) and ends with ejaculation in the vagina (a concrete external act). But this account is both too vague and too narrow.

To say that sex begins with arousal is like saying that eating begins with appetite. Meanwhile, to define sex as culminating solely in vaginal ejaculation is arbitrary and inadequate. For instance, men can have orgasms without ejaculation, as shown in tantric practices or dry orgasms. Are these acts therefore not “sex” under natural law?

Feser even allows, in The Last Superstition, for certain forms of oral sex as foreplay—so long as the final act is penile-vaginal ejaculation. But what counts as foreplay, and how far can it go? Would anal foreplay be permitted if it led to vaginal ejaculation? What if one starts foreplay but is interrupted before climax? Must the act be completed to avoid “perversion”?

3. Interruptions and Intentions: When Is Sex Permissible to Stop?

Imagine I need to urinate during intercourse. I stop, go to the bathroom, return—and the mood is gone. Am I morally obligated to finish what I started? What if a fire breaks out? Or a baby cries? Can I abort the act even at the point of climax?

These scenarios reveal how fragile the Thomist framework is when faced with real human situations. If ejaculation outside the vagina is always immoral, are there any justifications for “interrupting” the act? If so, what are they? Where are the lines? The framework demands precision but offers none.

4. Questions of Anatomy and Gender

If moral judgments are grounded in anatomy and teleology, troubling questions arise:

• Does a woman’s clitoris—having no direct procreative role—exclude her from full participation in the sexual act’s "telos"?
• Do women have a different moral status in natural law based on their anatomy?
• What about intersex people, or men with diphallia (two penises)? Are both organs moral if one is infertile?
• Can a man sin by ejaculating purely from erotic fantasy, without any physical stimulation?

What, exactly, is being perverted when no “generative” opportunity is missed?

5. The Absurdity of Rigid Sexual Teleology

Natural law often treats ejaculation as the decisive moral event. But in many cases—like karezza (coitus reservatus) or micro-penis intercourse—the entire framework breaks down.

Or consider a man dreaming: someone touches him sexually in his sleep, and he ejaculates. Has his generative faculty been "perverted"? The absurdity is obvious. Thomism cannot account for involuntary, incomplete, or non-procreative expressions of sexuality without collapsing into contradictions.

Even Grisez admits that inducing vomiting is not wrong if there's a good reason. So why not allow similar reasoning for ejaculation? Clearly, it’s not the act itself that offends, but the intent and context—yet natural law insists on the intrinsic wrongness of "perverted" faculties.

6. Hands, Kisses, and Teleological Chaos

"Therefore the will-to-know, objectively perceived, is the brain, just as the will-to-walk, objectively perceived, is the foot; the will-to-grasp, the hand; the will-to-digest, the stomach; the will-to-procreate, the genitals, and so on." (Arthur Schopenhauer, The World as Will and Representation, Volume II, Chapter XX)

From this perspective, the function of the hands, when viewed through the lens of natural law, appears inherently constrained—perhaps limited primarily to grasping. A Thomist philosopher could not dismiss this interpretation with unequivocal certainty. Indeed, one might argue that the hands possess multiple specialized principal functions, contingent upon context, including grasping, striking, stroking, scratching or poking with the fingers, signaling, and—in culturally evolved contexts—gestures of welcome. To assert that the hand lacks any specialized function and instead serves a universal purpose is to engage in mere evasion or rationalization. The apparent universality of the hand's utility arises not from intentional design but from its contingent anatomical structure. By analogy, the eyes exhibit no such universality in their application, though one could envision, in the realm of imagination, ocular faculties with far broader capabilities.

7. Homosexuality and Homoeroticism in Natural Law

Natural law typically condemns homosexuality on the grounds that it lacks reproductive potential. But this is problematic:

• Post-menopausal heterosexual sex also lacks reproductive potential.
• So does sex between infertile heterosexual couples.
• Yet these acts are not condemned.

Why the inconsistency?

As Andrew Koppelman argues:

“If heterosexual sex between infertile people is not immoral, then why is homosexual sex? Both acts lack reproductive potential.”

One might even argue that homosexual partnerships fulfill the relational telos of sexuality more fully than some heterosexual ones. Plato saw true love as possible only between men. Aristotle, too, treated pederasty as socially accepted in various cultures. Schopenhauer and Weininger likewise acknowledged the normality of homosexual variation.

What, then, does it mean to call homosexuality “unnatural”? Weininger already noted in 1900 that sexuality exists on a spectrum, with every human having elements of both masculinity and femininity—and, therefore, of homo- and heterosexuality.

Even Catholic Thomists like Mark D. Jordan have openly embraced this tension. Jordan, a leading scholar of Aquinas and now professor at Harvard Divinity School, argues that Thomism’s objectivist methodology allows closeted gay thinkers to flourish precisely because it removes the subject from view.

8. The Ethical Blind Spot of Objectivist Thomism

This is Thomism’s great strength—and its great weakness: it speaks from above, not below. It does not begin with lived experience, but with abstract essences.

As Nicholas Capaldi notes:

“Revived Thomism... blocked adequate consideration of interiority or the inner domain.”
(Capaldi, The Death of Metaphysics)

Thomism bypasses the modern turn to subjectivity inaugurated by Descartes and deepened by phenomenology. In doing so, it misses the richness—and moral relevance—of human interior life.

9. Conclusion: The Cracks in the System

Thomistic natural law offers the appearance of rigor and coherence, but it falls apart under closer analysis. It cannot:

• Define sex with precision,
• Account for real-world complexity,
• Handle intersex or non-reproductive bodies consistently,
• Offer morally compelling criteria for interruptions or exceptions,
• Reconcile its treatment of homosexuality with its broader claims,
• Or explain why reproduction must remain the defining feature of sexual ethics.

What remains is a fragile edifice built on selective biology, questionable metaphysics, and outdated cultural assumptions. Natural law, in this rigid form, seems less like a moral compass and more like a relic of a world that feared complexity, ambiguity, and desire.

Homosexuality and the Fragility of Natural Law Reasoning

1. Partnership and Teleology

The idea that a loving, stable partnership—where two people meet at eye level—is the true telos of intimate human relationships is arguably more realized in many homosexual relationships than in heterosexual ones. Plato, for instance, famously idealized love between men as the highest form of erotic and philosophical intimacy.

Under natural law theory, however, same-sex relationships are typically dismissed due to their lack of procreative potential. But what if the partnership aspect of a relationship—not its procreative function—is itself morally meaningful? Most of life in a committed relationship is lived outside the bedroom. Is it not reasonable to propose that love, care, and mutual support form a teleology of their own—one that same-sex couples can fulfill just as, or even more, effectively than heterosexual couples?

To deny this dimension while fixating solely on reproduction is reductive.

2. Homoeroticism and Hypocrisy

Even if natural law condemns homosexual acts, it cannot easily reject homoeroticism more broadly—tenderness, aesthetic attraction, and deep emotional bonds between people of the same sex. Plato and Aristotle both acknowledged same-sex sensuality. In The Symposium, Socrates’ refusal of Alcibiades' advances is treated not as moral condemnation, but as heroic restraint.

This raises an absurdity: if homoerotic affection is permitted, why the moral panic when it “goes too far”? If there is no persuasive argument against homoeroticism in theory, why the outrage in practice?

Would Catholic critics be more comfortable if homosexual couples adopted children after sex? Would this retroactively justify the act because it points vaguely toward procreation? The inconsistency is hard to ignore.

And if a man behaves effeminately, does he violate natural law simply by distancing himself from stereotypical masculinity? These questions expose the fragility of the gender essentialism at the heart of natural law theory.

3. Historical Context and Shifting Norms

Schopenhauer offers revealing insights into ancient attitudes. In classical Greece, love between older men and younger boys—pederasty—was treated not only as normal but often as morally praiseworthy. Socrates speaks approvingly of it in Xenophon’s Memorabilia. Aristotle references it in Politics as a custom accepted among Celts and Cretans. There was no consensus that this love was "unnatural."

Otto Weininger, writing in the early 20th century, argued that no sharp division exists between male and female, but rather a spectrum of “intermediate sexual forms.” Homosexuality, for him, was a natural expression of these forms—not a pathology or moral failing. His radical conclusion: every human being contains both homosexual and heterosexual potentials.

4. The Procreation Problem

The central natural law argument against homosexuality is its supposed failure to fulfill the procreative function of sex. Yet Catholic doctrine does not consistently apply this logic.

If procreation were a necessary condition for moral sex, then intercourse:

• during infertility,
• with postmenopausal women,
• or between a fertile and infertile partner

would also be immoral. But these acts are generally permitted. The distinction between "essential" and "accidental" infertility, made by Aquinas in Summa Contra Gentiles, appears increasingly artificial. Homogenital acts are labeled “essentially” non-procreative, while infertile heterosexual sex is treated as only “accidentally” so—even when both are equally incapable of resulting in conception.

T. M. Murray rightly questions the logic:

“Why must procreation remain the moral criterion, when we now know so much more about the emotional, psychological, and relational dimensions of sexuality?”

Andrew Koppelman further dismantles the inconsistency:

“There is nothing in nature that dictates we draw lines the way natural law insists we must... even if heterosexual sex is normal, it doesn’t follow that it is normative.”

He illustrates this with a powerful analogy: a sterile person’s genitals are no more procreative than an unloaded gun is deadly. Just as pulling the trigger on an empty gun is not a homicidal act, neither is sex between non-procreative partners intrinsically reproductive.

Thus, the act’s intention, context, and capability all matter more than formal structure.

5. Thomism’s Objectivist Blind Spot

The clash between homosexuality and natural law becomes particularly sharp within Thomist circles. As theologian David Berger recounts, many Thomists he encountered were themselves gay—but lived closeted, conflicted lives within a tradition that condemns them.

Only a few, like Mark D. Jordan, have publicly reconciled their identity with their intellectual commitments. Jordan’s case shows how Thomism’s objectivist and self-effacing style—“The thing must speak, not the person”—allows personal identity to disappear from theological discourse. In this context, the gay Thomist finds a peculiar shelter: able to think and teach freely, as long as he remains silent about who he is.

Berger observes that Thomism's silence on the subjective—its lack of interiority, of autobiographical dimension—provides cover for such double lives. Aquinas himself never wrote like Augustine. There are no confessions, no personal doubts, no visible sins. This distance may be why Aquinas was canonized so quickly: he offered a theology without a person.

But this philosophical posture comes at a cost. As Nicholas Capaldi argues, neo-Thomism’s resistance to modern subjectivism—especially as developed through phenomenology and post-Kantian philosophy—has blocked any serious engagement with interiority and the emotional reality of moral life.

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Conclusion: What Is Natural, and for Whom?

Natural law claims to define what is “natural” for humans. But whose nature does it describe?

• Is it the nature of postmenopausal women?
• Of intersex individuals?
• Of celibate priests?
• Of gay Thomists?

The insistence on reproductive potential as a universal moral standard ignores the vast range of human sexual and emotional life. Worse, it imposes a rigid, taxonomic morality on bodies that do not conform—and never have.

A system that allows no space for real human variation, and no engagement with lived experience, cannot be called universal. It is, at best, an idealized abstraction. At worst, it becomes a tool of moral exclusion.

If Aquinas were alive today, aware of modern science, psychology, and lived experience, would he still argue that the moral worth of love rests solely on whether semen enters a vagina? It seems unlikely.

As our understanding of human sexuality expands, so must our ethical frameworks. The task is not to discard reason or tradition, but to bring both into honest conversation with reality.

Internal Attitude or Outward Appearance

Christian ethics, particularly as expressed in the Sermon on the Mount, diverges sharply from the framework of natural law. The Sermon emphasizes an ethics of internal attitude and compassion rather than external conformity to natural faculties. In Matthew 5–7, murder is equated with harboring anger, and adultery with a lustful gaze. These teachings are incompatible with a naturalistic teleology that grounds moral judgment in the function of biological organs.

The Golden Rule (Matthew 7:12), appealing to personal will and empathy, similarly lacks alignment with natural law ethics, which relies on an objective, function-based morality. Natural law tends to focus on the outward execution of actions, often sidelining the internal intentions of the moral agent. Thomistic discourse oscillates ambiguously between prioritizing internal attitude and external form, rarely providing a consistent hierarchy between them.

Consider a person who abides by natural law solely out of fear of hell. Kant would argue such a person acts in conformity with duty, but not from duty—a key moral distinction. Yet natural law often concerns itself more with whether the external order of nature is upheld rather than with the agent's inner moral disposition.

This inconsistency is especially evident in Catholic moral teachings about contraception. Two couples may share the same intent to avoid pregnancy, but if one uses condoms and the other uses the rhythm method, only the former is considered sinful. The biological effectiveness and purpose of both methods are nearly identical, yet one is condemned based on its artificiality, despite both being rooted in a shared internal disposition. Conversely, suicide and martyrdom differ not in external form but internal intent, and yet only the latter may be morally justified.

The Church allows "natural family planning" (NFP), yet prohibits artificial contraceptives. The justification often hinges on preserving an external natural order. But this distinction becomes arbitrary when the intention remains the same: avoiding pregnancy. NFP requires scientific tools, charts, and calculations, relying heavily on technology and artificial aids. Meanwhile, condoms are made of natural materials. Thus, calling one "natural" and the other "unnatural" is inconsistent.

Some conservative Catholics even accuse NFP users of abusing the method when they use it to limit children. If intent is central, then both NFP and condom use can equally reflect a contraceptive mindset. The act of engaging in sex without the desire for procreation seems morally suspect to natural law theorists, regardless of the method.

Martyrdom versus suicide presents another inconsistency. Jesus teaches (John 15:13) that laying down one's life for a friend is the greatest act of love. But natural law deems all suicide inherently immoral. If external form alone determines morality, then martyrdom and suicide are indistinguishable. Nietzsche observed that Christianity permitted only two forms of suicide: martyrdom and ascetic self-denial. This selective approval reveals a theological, not naturalistic, bias.

"Other Than" vs. "Contrary To" Nature

Natural law claims that misuse of faculties contrary to their natural ends is immoral. But using a faculty for a non-procreative purpose (“other than”) is not always immoral. For example, chewing gum, walking on hands, or playing football can all deviate from the "proper" function of body parts, yet are not considered immoral unless damage occurs. Harm or intent to harm might be necessary to define what constitutes a "contrary to nature" action.

But then the line blurs. If I chew gum with the intent to prevent digestion, is that immoral? If I use my sexual faculties purely for pleasure, with no intent to frustrate procreation but full knowledge that it will not occur, does that make my act immoral? Is it enough to foresee non-procreative consequences for the act to be condemned?

Thomistic ethics suggests one need not intend the proper end, but must not thwart it. This asymmetric standard seems incoherent. Once I know my act cannot result in procreation (e.g., due to sterility), then choosing to engage in sex anyway seems necessarily to involve a thwarting of the natural end.

Knowledge, then, becomes crucial. If I know my action thwarts procreation, does that make it immoral? But knowledge and intent are slippery. I might act with one intention (fun) and foresee another consequence (non-procreation) without willing it. This produces a tension between moral knowledge and moral guilt.

Sex with Sterile People

Natural law fails to convincingly distinguish between contraceptive and sterile sex. Consider a man who seeks sterile women to satisfy his sexual desires without pregnancy risk. This is no different, in intent or result, from using condoms. Similarly, if a married couple avoids sex except during infertile periods or is permanently sterile, the intention remains the same: sex without reproduction.

Some natural law theorists argue that sex with a sterile spouse is acceptable if it conforms externally to procreative sex and occurs within loving marriage. But this introduces arbitrary criteria—love, marriage, and the mimicry of fertility—none of which are biologically grounded. These criteria are spiritual and theological, not naturalistic.

Moreover, these criteria do not apply elsewhere. A blind person need not pretend to see. A woman without milk glands need not pretend to breastfeed. Why must sterile couples pretend their sex is procreative? This elevates form over substance and implies a spiritual essence to sex that is beyond the scope of natural law.

Contraception and Symmetry of Intention

Numerous scenarios expose the inconsistency of natural law:

1.     A woman uses hormonal contraception for health reasons. Her partner knows and still has sex.

2.     A woman is permanently sterile. Her partner knows and has sex out of love.

3.     A woman uses NFP to avoid pregnancy. Her partner cooperates.

In all cases, the couple intends non-procreative sex. If intention matters, then all three acts are equally problematic. If external form matters, then why permit sex with sterile women but not with contraceptive users?

The Thomist response that intention matters only sometimes, or that marriage sanctifies sterile sex, fails to address the core inconsistency. The moral relevance of intention fluctuates based on the Church's doctrinal needs, not a consistent moral framework.

Masturbation

Thomists typically condemn masturbation as perversion. But if intention is not to thwart reproduction but to relax, explore, or self-soothe, then it constitutes an "other than" rather than "contrary to" use. Masturbation can have many psychological and health benefits, and often involves no intention to frustrate procreation.

Indeed, from a psychological perspective, there may be little difference between masturbation and sex with a contraceptive-using partner. In both cases, pleasure is sought without reproduction. If natural law permits sex with sterile people under certain conditions, it must also consider that masturbation might be morally neutral or even good.

In conclusion, natural law ethics—especially in its Thomistic form—fails to maintain consistency in its treatment of intention, external form, and function. It arbitrarily condemns or permits acts based on theological, rather than naturalistic, considerations. Its supposed grounding in nature dissolves when applied across cases with similar intentions but different technicalities. The distinction between "other than" and "contrary to" collapses under scrutiny, leaving a system riddled with inconsistencies, contradictions, and theological special pleading.

Final Words and Reflections: On Suicide and Bestiality

The Decline of Thomistic Natural Law

Thomistic natural law ethics no longer resonate with contemporary sensibilities. Its doctrines, once dominant, have lost much of their moral authority. Personally, I cannot bring myself to morally condemn either homosexuality or suicide—both considered grave sins under natural law—because I simply do not perceive the absolute moral reprehensibility that natural law theorists claim.

A true adherent of natural law must loudly uphold its moral judgments, even at the cost of social isolation. But I find greater moral clarity and emotional resonance in alternative perspectives—especially on the subject of suicide.

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On Suicide: Perspectives from Schopenhauer and Nietzsche

Arthur Schopenhauer offers a powerful defense of suicide as a rational choice:

“There is nothing in the world to which everyone has such an indisputable right as his own person and life.”
(Schopenhauer, §157 On Suicide, Parerga and Paralipomena Vol. 2)

He continues:

“Duties of right towards ourselves are impossible… What I do is at all times what I will, and consequently never a wrong.”
(Schopenhauer, The Two Fundamental Problems of Ethics)

In the same spirit:

“The news of a suicide evokes sorrow and often admiration for the person's courage, not the moral outrage elicited by murder or theft… Who has not known someone who chose to depart this world voluntarily? Are we to think of them with revulsion? I say no—and no again.”
(Schopenhauer, §157 On Suicide)

He rejects religious and philosophical objections as weak:

“Is Hamlet’s monologue the meditation of a crime? The objections to suicide proposed by monotheistic religions and their friendly philosophers are weak sophisms, easily refuted.”
(Schopenhauer, §157 On Suicide)

Friedrich Nietzsche echoes and extends this line of thought:

“The two greatest judicial murders in world history—Jesus and Socrates—are, without exaggeration, concealed suicides. In both cases, the man willed to die.”
(Nietzsche, Human, All Too Human II)

And further:

“Natural death is irrational—a suicide of nature. Suicide, by contrast, may be a rational act of liberation. Religious faith may obscure this clarity, but outside of that context, suicide can be a triumph of reason.”
(Nietzsche, Human, All Too Human II)

He concludes provocatively:

“Why should an old man, aware of his decline, prolong his suffering rather than consciously set a limit to his life? Suicide in such a case is natural and even noble.”
(Nietzsche, Human, All Too Human)

Fritz Mauthner challenges the very framing of the question:

“Asking whether suicide is allowed is as senseless as asking whether an oak tree is allowed. Man is part of nature, even in death. Suicide is not unnatural—it is a part of nature’s own expression.”
(Mauthner, Wörterbuch der Philosophie)

He proposes a shift in language from Selbstmord (self-murder) to Freitod (free death), freeing the act from the criminal implications of the former term.

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Ethical Conclusion on Suicide

Given these perspectives, there is no compelling moral reason to condemn suicide. However, this does not mean suicide should be encouraged or accepted without question. In most cases, it emerges from a temporary state of despair, hopelessness, or mental illness. It must be prevented where possible—compassionately and with care. For a deeper philosophical discussion, David Hume’s essay on the subject is also highly recommended:
https://www.earlymoderntexts.com/assets/pdfs/hume1757essay3.pdf

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On Bestiality: Between Perversion and Morality

Today, homosexuality is rightly accepted as a natural variation of human sexuality. Bestiality, however, remains deeply taboo—often labeled as perverse. And while I agree that it is highly perverse, I do not consider it morally evil per se.

One does not need natural law to reach this conclusion. Bestiality ranks high on the scale of sexual perversity—perhaps higher than urophilia—but perversity is not equivalent to moral wrongdoing. As long as no being is treated merely as a means, acts along this scale can avoid moral condemnation. Still, bestiality is, in my view, a psychological matter. A person engaging in it is likely not well, and likely not happy. The risk of disease and social isolation adds further weight against it.

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Understanding Sexual Perversion

Whether a sexual act is natural or perverse has less to do with which organs are involved, and more to do with the psychology behind the encounter. Several philosophers provide insight here:

“Sexual behavior differs from other behavior by its unique feelings, emotions, and its capacity to create shared intimacy.”
(Janice Moulton, “Sexual Behavior: Another Position” in The Philosophy of Sex, ed. Alan Soble, 2002)

Thomas Nagel sees sexual desire as a mutual perception between partners. When this reciprocity is missing, the experience becomes truncated—and thus perverse.

Robert Solomon, similarly, maintains:

“The end of this desire is interpersonal communication, not merely enjoyment.”
(Moulton, summarizing Solomon)

Bertrand Russell distills the moral dimension:

“Morality in sexual relations, when free from superstition, consists essentially in respect for the other person and in an unwillingness to use that person merely as a means for personal gratification.”
(Russell, Marriage and Morals)

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Bestiality Revisited

Neil Levy raises a powerful social argument:

“Those who engage in bestiality distance themselves from the community as it currently defines itself. Such acts threaten one’s identity as a full member of that community.”
(Levy, “What (if Anything) Is Wrong with Bestiality?” in Journal of Social Philosophy, 2003)

He concludes:

“Though there is nothing intrinsically immoral about bestiality, it may nevertheless be irrational for us to cross that boundary.”
(Levy, 2003)

As someone who rejects natural law, I am free to draw insights from nature without grounding morality in it. And it should be clear why bestiality—like masturbation—is unsatisfying for those who seek shared emotional intimacy, mutual affection, and deep existential connection. Masturbation is a stand-in for a real sexual partner, and this is reflected in fantasy. Similarly, bestiality offers only a hollow substitute for the rich human experience of mutual love.

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Closing Thoughts

Both suicide and bestiality remain controversial topics, but they require clear-eyed, non-dogmatic discussion. Suicide may be tragic, but it is not necessarily immoral. Bestiality may be perverse, but not necessarily evil. Both topics challenge conventional ethical boundaries—and thus call for careful philosophical reflection grounded in reason, empathy, and psychological insight.