Philosophy needs literature more than literature needs philosophy. Of course literature does not need philosophy at all. In each of the three origins of philosophy—Greek, Indian, and Chinese—literature preceded philosophy, and the first philosophers were so concerned with literature that, in ontogeny, philosophy and literary criticism are difficult to distinguish.
But philosophy's need for literature is more than genealogical. Philosophy is a project of discovery, not invention. A philosopher who only demonstrates something that we could believe about the world and about our place in it is, as a philosopher, a failure. Rather, in order to live, a philosophy must show that it has always been what people believed, though they did not yet know it. For such unknown beliefs literature is the only body of evidence.
A philosopher must also account for how false beliefs come to be; again, only literature shows the range of what it is possible to believe, records the means by which false beliefs spread and develop, and preserves the occasion and substance of their error.
Of course, the last few centuries have more often invoked mathematics or science than literature. And I cannot call this is a decline or aberration, because more philosophy has been done in them than had been done in all history before. But the question must be asked: does philosophy, in approaching mathematics or science, receive them as mathematics and science; or does it coerce the statements of mathematics to a literature of mathematics, the statements of science to a literature of science?
We know that philosophy in relying on mathematics has often fallen apart when mathematics shifted beneath it—most infamously in Kant's now-embarrassing reliance on the uniqueness of Euclidean geometry. Yet philosophers are more often mathematical than scientific. Locke, philosopher, faced with the depths of Newton's Principia, asked Huygens, mathematician, whether he could trust its proofs implicitly. On Huygens's word Locke, founder of modern philosophy, read the foundational work of modern science by skipping the proofs, reading from result to result. This seems representative.
Consider philosophers (and artists too) trying to digest relativity or quantum theory, declaring the advent of a new world, pledging themselves to it, raising its banner—philosophers (and artists) who could not tell Feynman's diagrams from Agrippa's sigils, who think a tensor belongs in a gym or a girdle.
But besides the significance of the results of science is the significance of Science itself as such. It's attraction for philosophers is obvious. Science can show something has always been true without having been noticed; it can show that what people always believed was simply false, and need not qualify or blunt its disproof. Fires have always burned by binding oxygen. This is true of every fire that ever burned; it is true of fires that burned before human beings lived; it is true of every fire human beings have ever kindled or set, whatever they looked into it and saw—the fire-god, the anagog of hell, the liberation of elemental fire, the release of phlogiston. Every fire, always, everywhere, forever. Science can deliver such eternities.
But the carcasses of philosophies based on obsolete science litter the last century. To learn from experience would be to notice that philosophy can learn from science only by expanding of the phenomena it must account for—only literarily—and that the attempt to join philosophy to science is at best a stunt, a balancing act.
This is not just because science is subject to shifts—of paradigms among others—but because even subtle drifts in terminology and in the emphasis of education can break—in natural building-up they must break—the link between a science and the philosophy supposedly based on it. The positivism that elides with foundations of mathematics is out of date, not because of Gödel or any other shock, but because the interesting work in foundations of mathematics is done and working mathematicians concern themselves with other things.
Philosophers are far harsher with philosophy than scientists would think to be. No would-be bicultural has ever delivered a blow to philosophy like Wittgenstein's sledgehammer. And scientists are far harsher with science than philosophers would dare to be. No would-be deconstructor has ever flensed the scientific method with Feynman's astringency.
So for philosophical purposes science is literature. How are other kinds of literature relevant to philosophy? How else does philosophy need literature? Ethics is the neediest of philosophical disciplines. Ethics as the study of virtue and vice, of the good life, is inextricably literary, and thus enfeebled by neglect. Instead we find everywhere in ethics the philosophical misfeasance of the moral paradox.
Moral paradoxes are not just experiments in lesser evils; they are evil experiments. It is absolutely irrelevant how a moral paradox is answered because the idea of a moral paradox is absolutely irrelevant to human beings. A moral paradox is a crisis without room for imagination. But imagination is how human beings do good. It is the only way in which human beings do good. I do not mean that both are evil choices; I mean that choosing is evil: that there is absolutely no more good in reasoning about moral paradoxes than in resolving them with dice. Of course moral paradoxes do happen. We are not always strong enough to resist or clever enough to escape them. But the proper treatment for those who would call one choice right and the other choice wrong is not to argue with them, but to beat them with sticks.
Kantian ethics, ethics practiced as pure reasoning, without consulting literature, are as vain, silly, and absurd as Aristotelian physics, physics practiced as pure reasoning, without consulting nature. The resemblance is not an analogy but an identity. Aristotelian physics refused to look outside itself to discover its real tasks, the phenomena it had to explain. Kantian ethics commits the same error.
As with physics, the phenomena for which ethics must account arrive from two sources. One is experiment; one is exploration. Experiment in ethics is singularly unreliable, because it must penetrate delusion; and adopting the vaunted methods of cognitive psychology is a mistake, not because there is anything wrong with experimentation or even cognitive psychology, but because the methods of cognitive psychology are exhausted and their application has become compulsive and rhetorical. Exploration is easier; it is already done. The reports of the explorers of the mind are stacked as high as the reports of explorers of seas and continents. Yet the map is permitted to remain blank, or it is drawn with some geometrical conceit, subs and supers, ectos and mesos, intros and extros, like old cartographers drawing pizza maps of the world with slices for continents, crust for ocean, and Jerusalem perched in the center holding up the lid. The cartography of the mind is an empty field; the geology that would unravel its tectonic rind, and which would really deserve the name of evolutionary psychology, is unthought. Someday the map must be filled; but the work must start as a kind of philosophy, and it must be informed by literature with some more urgent use than illustration.