Hume, Naturalist

 We tend to assume that Deism arose in the 18th century because it was the only available position for an enlightened skeptic to take. Outright atheism was, at the time—we suppose—virtually unthinkable; and not only because of the social opprobrium against it; but also because of the argument from design. In an era before the Darwinian theory of evolution, people could not frame any account of how lifeforms in the universe had come to be so well-adapted to their environment; unless—that is—they had been made that way, by some sort of wise, watchmaker deity who had set the whole thing in motion. 

I was reading Hume's Dialogues Concerning Natural Religion for the first time, however (or maybe not for the first time—perhaps I attempted this in college; I can't really remember—at any rate, I got a lot more out of it this time)—and I discover that Hume (speaking through the voice of his skeptical agonist Philo in the dialogue form) actually foresaw roughly how an evolutionary account of the formation of well-adapted life might go. Here—a century before Darwin wrote his great works—Hume already gestured toward the principle of natural selection as an explanation of animal adaptation. 

Hume, to be sure, is careful not to plump for this theory (as he is careful not to plump for anything too overtly in the Dialogues that would lower the mask of authorial inscrutability). But his skeptical character Philo does lay out a version of a materialistic "Epicurean" cosmology that could explain all the well-adapted features of life that appear to so many humans as evidence of "intelligent design" in the universe. Suppose, he says, that matter originally in the universe formed a kind of swirling chaos. It would congeal into a multitude of unstable forms that would disperse—but we wouldn't know of them. 

The only forms of matter we would experience would be the ones that had somehow managed to survive this great repeated series of formations and dispersals. And so, the same would be true of animals. The ones that have survived may appear to us to be so well-adapted to their setting that they must have been deliberately built that way. But—Hume points out—it could be that innumerable less-adapted forms preceded them; but we'd never know of them—simply because they wouldn't have survived. By definition, the animal forms that were not well suited (or "fit") would have long since perished. 

We have here, then, basically the whole central idea of "survival of the fittest" and "natural selection"—again, a century before Darwin. Long before the Beagle's naturalist, Hume had already perceived his core insight. "It is in vain," Hume writes, "[...] to insist upon the uses of the parts in animals [...] and their curious adjustment to each other. I would fain know how an animal could subsist, unless its parts were so adjusted? Do we not find, that it immediately perishes whenever this adjustment ceases[?...] Must it not dissolve [...] till in a great, but finite succession it fall [...] into the present or some such order?"

Of course, Hume did not perceive the role that heritability of traits across generations would play in making this alternative account of adaptation persuasive. That insight justly belongs to Darwin and Wallace. Hume could not have arrived at a fully-worked out version of natural selection—in part because he believed that species forms were essentially fixed over time. He thought that each species was so well-tuned to its environment, that it would perish under the slightest alteration. Consistent with this, he also states in one passage that probably no species has ever gone extinct in the history of animal life. 

However, even here, Hume had such a genius for thinking up rival hypotheses, that he expressly admits the possibility that some species may actually have died out over time. Not only that—but he cites an example of species extinction that we would still recognize today as canonical: the elimination of the aurochs—a type of massive, horned cattle—from Europe. Hume observes—in a manuscript note he later cancelled—that Caesar refers to a mysterious creature, in his book on the Gallic wars, that no longer appears to exist. The Caesar passage, in turn, appears to describe the aurochs. 

Hume, then, with none of the benefits of modern empirical science or the observations of naturalists, was able to arrive at something much like the insights of Victorian biology with only a few volumes of Cicero, Caesar, and Lucretius for aid. He was just that clever!

Of course, in spite of Hume, in spite of Darwin, in spite of centuries of thought on this—people still today walk into the same anthropocentric fallacies that Hume debunks in the Dialogues. They still cite the argument from design as if it were the only explanation of reality; without heeding Hume's objection that it really explains nothing, and only pushes back the explanation by a peg. They still reason, from the "fine-tuned" adaptation of life to its cosmic and Earthly environment, that the latter must have been adapted to us, rather than the other way around—i.e., that we are in fact adapted to our cosmos. 

And in the endless speculations about extraterrestrial life, touched off by spurious "revelations" of a government UFO program, etc.—people still reason as if the universe could only be made in our own image. If life exists on other planets, people assume that it must build technology like we do—that it must have spaceships just a couple degrees more advanced than our own. In an earlier blog, I quoted Roland Barthes's observation condemning this anthropic fallacy about UFOs: the bogus assumption, as he put it, that "Martian history [must have] ripened at the same rhythm as that of our world." (Howard trans.)

And here I find that Hume already came to the same insight:

Is there any reasonable ground to conclude, that the inhabitants of other planets possess thought, intelligence, reason, or any thing similar to these faculties in men? When nature has so extremely diversified her manner of operation in this small globe; can we imagine, that she incessantly copies herself throughout so immense a universe? [...] The narrow views of a peasant, who makes his domestic oeconomy the rule for the government of kingdoms, is in comparison a pardonable sophism. 

Mankind stands gazing up at an immense universe, and—with understandable partiality—assumes it must have been made with his needs in mind, by a Being that resembles him, and that—if any other stars might contain their own forms of life—these must likewise be made in his image. Centuries after Hume, we still have not rid ourselves of this same anthropocentrism. Many still believe in "intelligent design" as opposed to evolution; many believe that aliens, if they exist in the universe, must build spaceships resembling those in our films—in short, that the entire cosmos must be built on a human model. 

In a later passage in his Dialogues—on this point—Hume refers to a certain mythological cosmogony that traces the birth of the universe to a giant spider. To modern Europeans, he writes, this may sound absurd. But, "were there a planet wholly inhabited by spiders (which is very possible), this inference [i.e., that the universe was spun out of a spider's belly]" he writes "would there appear as natural and irrefragable as that which in our planet ascribes the origin of all things to design and intelligence." 

As another great Enlightenment skeptic (Volney) put it—writing not long after Hume: 

Contemplating the picture which he hath drawn of the Divinity: No, said I, it is not God who hath made man after the image of God; but man hath made God after the image of man; he hath given him his own mind, clothed him with his own propensities; ascribed to him his own judgments. And when in this medley he finds the contradiction of his own principles, with hypocritical humility, he imputes weakness to his reason, and names the absurdities of his own mind the mysteries of God. (Eckler trans.)