In his book Miracles, C. S. Lewis takes aim at “naturalists” who say that there is no “outside” reference [i.e., God] for calling anything good or evil.On naturalism there are no moral obligations and thus the word "ought" has no moral significance. If there are no moral duties then there's nothing anyone "ought" to do, at least not in the moral sense of the word "ought."
When men use the words, “I ought,” Lewis notes, they are saying something about the essence of right and wrong that is built into the universe. In fact, naturalists should never use such terminology: “But if Naturalism is true,” he writes, “‘I ought’ is the same sort of statement as ‘I itch’ or ‘I’m going to be sick.'”
The Naturalist can, if he chooses, brazen it out. He can say . . . “all ideas of good and evil are hallucinations—shadows cast on the outer world by the impulses which we have been conditioned to feel.” Indeed many Naturalists are delighted to say this.There’s a slight problem, though, for those who attempt to explain good and evil in this way:
But then they must stick to it; and fortunately (though inconsistently) most real Naturalists do not. A moment after they have admitted that good and evil are illusions, you will find them exhorting us to work for posterity, to educate, revolutionise, liquidate, live and die for the good of the human race. . . . They write with indignation like men proclaiming what is good in itself and denouncing what is evil in itself, and not at all like men recording that they personally like mild beer but some people prefer bitter.Of course, if good and evil are illusions then there's certainly no reason why we should be concerned with either the illusion of good or the illusion of evil.
To use such terms when the user knows they don't refer to anything is a form of social coercion. Naturalists who employ the rhetoric of good and evil are simply attempting to compel, or trick, others into behaving in ways the naturalists prefer by calling their actions good or evil when in fact they're neither good nor evil - no more than are the actions of a wolf or falcon or any other predator. When one gull steals a morsel of food from another we don't call the gull or its behavior evil. Likewise, if we're just animals, if there's no transcendent moral order, why do we call evil acts like robbing an elderly lady?
Do they remember while they [naturalists] are writing thus that when they tell us we “ought to make a better world” the words “ought” and “better” must, on their own showing, refer to an irrationally conditioned impulse which cannot be true or false any more than a vomit or a yawn?Yet, as Snyder points out, the naturalist, unless he's also a nihilist, doesn't live consistently with his own professed ideology. Snyder concludes with another quote from Lewis:
My idea is that sometimes they do forget. That is their glory. Holding a philosophy which excludes humanity, they yet remain human. At the sight of injustice they throw all their Naturalism to the winds and speak like men.Yes, they do, but when they do they admit the failure of their naturalism. A worldview that people can't live with consistently is seriously flawed.