Lewis, Aristotle, and Practical Reason

In some previous posts, I have argued that a Darwinian science of morality and politics could satisfy C. S. Lewis's call in The Abolition of Man for a "new Natural Philosophy" that could explain the human nature of morality (89).

Lewis seemed to reject the possibility of an evolutionary ethics, however, in his criticisms of C. H. Waddington's essay "Science and Ethics" (49-50). Lewis quotes Waddington's claim that "existence is its own justification," and "an existence which is essentially evolutionary is itself the justification for an evolution towards a more comprehensive existence." To Lewis this illustrates the futility of trying to infer moral values from natural facts. If we praise evolution for any property that we deem praiseworthy, then we are implicitly using an external standard of judgment, and thus denying our premise that "existence is its own justification." But if we stick with this premise, then we will have to say that "good" means "whatever Nature happens to be doing," which will not support the value judgments that human beings actually make.

Lewis's criticisms of Waddington are persuasive. I can agree that we cannot rightly judge any human behavior good simply because it has evolved.

But it does not follow from this that our judgment of some human behavior as good is not a product of the natural evolution of our species, which is what G. E. Moore did when he identified "good" as an indefinable, non-natural property. It does not follow that moral values are non-natural facts existing in some transcendental realm beyond ordinary human experience. Rather, we can conclude that moral values are subjective facts of our evolved human psychology.

The most common objection to evolutionary ethics is that it commits the "naturalistic fallacy" by ignoring the is/ought or fact/value dichotomy that was first identified by David Hume. But this is mistaken, because far from separating facts and values, Hume showed how moral judgments could be grounded in certain facts of human nature. This explains why Darwin incorporated Hume's theory of the moral sense into his evolutionary account of human morality.

Hume's claim is that moral distinctions are derived not from pure reason alone but from a moral sense. This idea can be traced back to Francis Hutcheson's criticisms of some early modern rationalists such as Samuel Clark and William Wollaston, who believed that moral distinctions could be derived from abstract reasoning about structures in the universe that were completely independent of human nature.

Far from denying that moral judgments are judgments of fact, Hume claims that moral judgments are accurate when they correctly report what our moral sentiments would be in a given set of circumstances. Moral judgments do not have cosmic objectivity in the sense of conforming to structures that exist totally independently of human beings. Yet neither do moral judgments have only emotive subjectivity in the sense of expressing purely personal feelings. Rather, moral judgments for Hume have intersubjective objectivity in that they are factual judgments about the species-typical pattern of moral sentiments in specified circumstances.

Hume compares moral judgments to judgments of secondary qualities such as colors. My judgment that this tomato is red is true if the object is so constituted as to induce the impression of red in normally sighted human beings viewing it under standard conditions. Similarly, my judgment that this person is morally praiseworthy is true if the person's conduct is such as to induce the sentiment of approbation in normal human beings under standard conditions. Just as an object can appear red to me when in fact it is not, so a person can appear praiseworthy to me when in fact he is not. The moral judgment whether some conduct would give to a normal spectator under standard conditions a moral sentiment of approbation is, Hume insists, a factual matter.

Thus, for Hume, moral judgment requires a combination of reason and passion. Reason can direct action, but it cannot motivate it. Passion is the primary cause of action because it sets the goals of action. Reason is the secondary cause of action because it provides information relevant to the goals set by passion.

Recent research in neurobiology confirms Hume's argument that reason and passion are distinct and yet complementary causes of human behavior, because rational conduct must be guided by emotional assessments that enforce a system of preferences. Any Kantian conception of moral rationality as utterly free from emotion has been refuted by neuroscience.

Aristotle's account of practical reasoning agrees with Hume and with this research in neuroscience in recognizing the primacy of passion or desire in motivating human action. "Thought by itself moves nothing," Aristotle believes, although reason can guide the desires that do move us. Desire always moves us, but thought never moves us without desire. Deliberate choice by practical reasoning requires a conjunction of desire and reason into "desiring thought" or "thinking desire." In his Rhetoric, Aristotle shows how the psychology of the moral emotions, working through social praise and blame, supports a natural moral sense.

Although Lewis does not cite Hume, he does employ Hume's comparison of moral judgments to perceptions of color, so that the moral truth of judging whether some behavior is truly praiseworthy or not is similar to the perceptual truth of judging whether some object is truly red or not.

Lewis does cite Aristotle, and clearly Lewis's account of "Practical Reason" as distinct from "Theoretical Reason" is drawn from Aristotle. Moreover, like Aristotle, Lewis sees that moral judgment requires a combination of reason with emotion, sentiment, or desire.

Moreover, Lewis's "Illustrations of the Tao" in The Abolition of Man are illustrations of the universal moral psychology of the human species as animals naturally inclined to feel moral sentiments of approval and disapproval.

One can see this by noticing how selective Lewis is in his choice of illustrations. For example, under the category of "the law of general beneficence," he quotes the Biblical injunction "Do not murder"(Exodus 20:13). Why doesn't he also quote these commands of Moses to his soldiers fighting against the Mideanites--"Kill all the male children and kill all the women who have ever slept with a man; but spare the lives of the young girls who have never slept with a man, and keep them for yourselves" (Numbers 31:17-18)? Doesn't he quote the first passage because he knows it will elicit the reader's sympathetic approval, while he knows that the second passage (or similar passages in the Bible) would provoke emotions of disapproval? Does that explain why the first belongs to "the Tao," but the second does not?

A Darwinian science of morality should be able to explain this moral psychology as rooted in evolved human nature. Such a science can make falsifiable predictions that are open to experimental testing. Much of the current research in evolutionary moral psychology is using experimental neuroscience, social psychology, and evolutionary game theory to do this.

Kantians like John Landon have objected to this post that I ignore the obvious fact that the Platonic Idea of the Good is beyond space and time. He offers no explanation as to why we should believe this. For him, this seems to be a matter of faith.