I am not a lawyer. I’m a political theorist, trained at the overlap of political science and philosophy. Still, I’m a proponent of natural law. Indeed, I have been since I first read the great English literary scholar C. S. Lewis on the matter (for instance, in The Abolition of Man). Years of studying ancient, medieval, and modern political thought have left me well disposed to Lewis’s argument. I winced, therefore, as I read F. H. Buckley’s caricatures of natural law and natural lawyers in his recent attempted take down. His essay advances an account of natural law advanced by no natural lawyer of my acquaintance and struck me as deeply unsound. Moreover, Buckley proposes replacing natural law with a radical ethical voluntarism that make good and evil wholly arbitrary and dependent on nothing but arbitrary omnipotent will or irresistible power.

In City of God, St. Augustine of Hippo recounts a tale (one probably adapted from Marcus Tullius Cicero) concerning the encounter of Alexander the Great with a Pirate. As Augustine tells it, Alexander the Great was sailing with his fleet one day when they happened upon a pirate. Having seized him, Alexander asked the pirate what he meant by infesting the seas. The pirate replied that he meant the same as Alexander, but whereas when Alexander infests the whole world with a great fleet and is called an emperor, when he (the pirate) does it with one small ship is called a robber. Reflecting on this event, Augustine writes,

Justice removed, then, what are kingdoms but great bands of robbers? What are bands of robbers themselves but little kingdoms? The band itself is made up of men; it is governed by the authority of a ruler; it is bound together by a pact of association; and the loot is divided according to an agreed law. If, by the constant addition of desperate men, this scourge grows to such a size that it acquires territory, establishes a seat of government, occupies cities and subjugates peoples, it assumes the name of kingdom more openly. For this name is now manifestly conferred upon it not by the removal of greed, but by the addition of impunity.

In her seminal essay, “On the Authority of the State,” British analytic philosopher (and Wittgenstein protégé) G. E. M. Anscombe suggests that Augustine’s position comes to this: justice is necessary for distinguishing a political association (a kingdom or a commonwealth) from sophisticated banditry. While the presence of justice is not sufficient for making the distinction, it is essential to it. The same goes for law. Thus, in De libero arbitrio (On the Free Choice of the Will), Augustine writes: “[T]hat which is not just seems to be no law at all.” Put another way, the presence of justice in the prescription is a necessary (albeit not sufficient) condition for distinguishing law from speech in the injunctive mode backed up by threat of sanction for non-compliance (the so-called strong man theory of law). Law requires more than justice and prescription, but, say both Augustine and Aquinas, it cannot get by with less.

The claim that justice is a necessary condition of law qua law has always been one of the central tenets of natural law—the idea that there is an objective, intelligible moral order built into the fabric of the world and, in particular, into human nature. In Western thought the idea of natural law is as old as Antigone’s invocation of the eternal, unwritten laws against Creon’s insistence that the ruler established by the city must be obeyed no matter what—whether what the ruler commands is big or small, just or unjust. Natural law has also had its critics, starting with Greek sophists who rejected the objectivity of the right and insisted that justice is purely conventional (and arbitrary). The sophist critique of natural law found new ammunition in the 18th century in the work of David Hume—in particular, in what we might call his insistence on the is/ought dichotomy, dubbed by G.E. Moore the naturalistic fallacy and framed as the proposition that it is impossible to derive an ought from an is. The implicit idea here is that Aristotelian ethics and Thomistic natural law are guilty of doing just this.

According to Hume,

In every system of morality, which I have hitherto met with, I have always remark’d, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surpriz’d to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ‘tis necessary that it shou’d be observ’d and explain’d; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be deduction from others, which are entirely different from it.

Hume apparently thinks that in every moral system he has so far encountered, when an ought is introduced, there is more in the conclusion than is contained in the premises. One notes (though Buckley does not) that for Hume this applies to divine command ontologies of moral obligation just as much as to Aristotelian or Thomistic accounts (Moore applied it in particular to utilitarianism). The voluntaristic “Augustinian” Buckley describes would be in as much trouble as the natural lawyer if Hume’s argument is both valid and sound. Fortunately it is not (certainly not in any kind of incontestable way that proponents of natural law are bound to take seriously).

Let’s note some startling implications of the Humean position. First, the is/ought dichotomy, as Hume frames it, eliminates ought entirely from among the things that are. That is, taken straightforwardly, Hume eliminates oughtnessand obligation altogether. And not just moral ought but every kind of ought. Indeed, either the is/ought dichotomy allows that there are such things as moral facts—and not just moral language facts but ought facts—in which case it is entirely innocuous with respect to natural law (i.e., it entails no criticism at all), or it eliminates oughtness and obligation from human life completely. Oughtness and obligation simply don’t exist (if there are no ought facts or if oughtness is built into the things that are). And that means moral analysis is never of actual obligations—on any recounting—but only, ever, of how ought language is used.

There are reasons for thinking Hume went in the direction of denying oughtness altogether—that is, of denying it beyond an analysis of the fact that we use such language. First, Hume is arguably the fountainhead of emotivism, of the idea that moral language calling some action virtuous or good is just a way of saying that it pleases us; calling an action vicious or evil or bad just a way of saying it displeases us. Moral judgments are just emotive expressions. But on emotivism (and expressivism more generally) our tastes are the only thing to which moral judgments ultimately refer. They are purely subjective. And, in that case, there’s no particular reason for preferring some judgments to others. Thus, Hume wrote,

’Tis not contrary to reason to prefer the destruction of the whole world to the scratching of my finger. ’Tis not contrary to to reason for me to chuse my total ruin, to prevent the least uneasiness of an Indian or a person wholly unknown to me. ’Tis as little contrary to reason to prefer even my ow acknowledg’d lesser good my greater, and a have a more ardent affection for the former than the latter.

Scratching my finger or the preservation of all humanity—there is no moral reason, on Hume’s position, for preferring the one to the other. There’s no moral reason for preferring saving a drowning baby to genocide on Hume’s account of rationality. Hume’s position entails radical normative skepticism.

Second, Hume’s is/ought dichotomy is tethered to his distinctive metaphysics and epistemology. Let’s begin with the latter. Hume holds that all knowledge comes from impressions—“from the immediate data of experience,” as Frederick Copleston puts it. Now, Hume introduces many distinctions—between impressions and ideas and between impressions of sensation and impressions of reflection. But the difference between impressions and ideas is a matter of “force and liveliness” or, as Copleston says, “vividness” rather than a difference in kind. Hume calls ideas “faint images” of “sensations, passions, and emotions” in “thinking and reasoning.” And impressions of reflection ultimately derive from ideas. Thus, Hume elaborates a thoroughgoing empiricist epistemology, which generates skepticism of the notion of substance and earlier “metaphysical reasoning.” His epistemology has a metaphysical agenda (which includes the rejection of Aristotelian and Thomistic metaphysics). But the price of Hume’s epistemology is steeper still.

In his Enquiry Concerning Human Understanding, Hume says that “all the objects of human reason” divide into two categories: relations of ideas and matters of fact. Relations of ideas include geometry, arithmetic, “in short, every affirmation which is either intuitively or demonstratively certain.” The truth with which these relations are concerned have nothing to do with existence, reality, or experience. Relations of ideas are “formal propositions, not empirical hypotheses,” says Copleston. Matters of fact, on the other hand, are simply matters of observation and experience. Propositions that are not either relations of ideas—purely formal and untethered to any truth about existence—or matters of fact—a matter of experience—are ones that we cannot know and of which we have reason to be skeptical. Now for Hume oughtness or obligation (in contrast to the use of ought language) is neither a relation of ideas nor a matter of fact. And so we have reason to be skeptical of any ought claim that goes beyond observations about how ought language is used (for instance, to express pleasure or displeasure). Instead of saying so much the worse for our knowledge of anything of consequence, we might instead say so much the worse for Humean epistemology. An epistemology that entails skepticism of the existence of God, the self, other minds, an external world has clearly gone wrong somewhere.  

This brings us, at last, to Hume’s metaphysics. Like moderns more generally, Hume rejects classical metaphysics. In particular, he rejects the ideas of formal and final causality. Consider final cause or telos. Aristotle and Aquinas hold that substances we encounter in everyday life are essences. And for something to be an essence just is for it to be ordered to an end, ordained to a goal. The things we encounter in everyday life have a proper function built into them. This is especially true when we look at something like the heart, the purpose of which is to circulate blood through the circulatory system, thereby providing life to the body. But goal directed behavior or functionality is as readily observable in eyes, livers, T-Cells, or various engines that operate within cells. Now for Aristotle and Aquinas, the good of anything is the performance or attainment of its proper function—and its highest good the performance of its proper function with excellence. As Alasdair MacIntyre argues in After Virtue, it is therefore possible to derive an ought from an is on a functionalist metaphysic—on an account of reality, that is, that includes final causation as part of the nature (essense or physis) of things. A necessary condition for holding that an ought can never be derived from an is is the rejection of final causality in metaphysics.

When it comes to theology, Buckley is right if he means to suggest natural law rejects a theology that understands God as sheer omnipotence or irresistible power beyond good and evil. He is right that natural lawyers reject the arbitrariness of good and evil. Rather, the theology of classical natural law is the traditional Christian identification of God and Goodness, of Goodness and God. But none of this has any implications (Pelagian or otherwise) as to our ability or tendency to observe the precepts of the natural law. As Lewis says at the end of Chapter 1 in Mere Christianity, “the foundation of all clear thinking about ourselves and the universe we live in” is that human beings “know the Law of Nature” and “they break it.”