How does [fill in the blank] in human affairs relate to the great central theory?

I do not, of course, mean any particular Great Central Theory. I am referring to the once-pervasive habit of relating everything that had human scale — Chinese history, the Odyssey, your mother's fear of heights — to an all-explaining principle. This principle was set forth in a short shelf of classic works and then worked to a fine filigree by close-minded people masquerading as open-minded people. The precise Great Central Theory might be, as it was in my childhood milieu, the theories of Freud. It might be Marx. It might be Levi-Strauss or, more recently, Foucault. At the turn of the last century, there was a Darwinist version going, promulgated by Francis Galton, Herbert Spencer and their ilk.

These monolithic growths had begun, I suppose, as the answers to specific questions, but then they metastasized; their adherents would expect the great central theory to answer any question. Commitment to a Great Central Theory thus became more a religious act than an intellectual one. And, as with all religions, the worldview of the devout crept into popular culture. (When I was in high school we'd say So-and-So was really anal about his locker or that What's-his-name's parents were really bourgeois.) For decades, this was what intellectual life appeared to be: Commit to an overarching explanation, relate it to everything you experienced, defend it against infidels. Die disillusioned, or, worse, die smug.

So why has this sort of question vanished? My guess is that, broadly speaking, it was a product of the Manichean worldview of the last century. Depression, dictators, war, genocide, nuclear terror — all of these lend themselves to a Yes-or-No, With-Us-or-With-Them, Federation vs. Klingons mindset. We were, to put it simply, all a little paranoid. And paranoids love a Great Key: Use this and see the single underlying cause for what seems to be unrelated and random!

Nowadays the world, though no less dangerous, seems to demand attention to the seperateness of things, the distinctiveness of questions. ''Theories of everything'' are terms physicists use to explain their near-theological concerns, but at the human scale most people care about, where we ask questions like ''why can't we dump the Electoral College?'' or ''How come Mom likes my sister better?'', the Great Central Theory question has vanished with the black-or-white arrangement of the human world.

What's next?

Three possibilities.

One, some new Great Central Theory slouches in; some of the Darwinians think they've got the candidate, and they certainly evince signs of quasi-religious commitment. (For example, as a Freudian would say you doubted Freud because of your neuroses, I have heard Darwinians say I doubted their theories because of an evolved predisposition not to believe the truth. I call this quasi-religious because this move makes the theory impregnable to evidence or new ideas.)

Two, the notion that overarching theory is impossible becomes, itself, a new dogma. I lean toward this prejudice myself but I recognize its dangers. An intellectual life that was all boutiques could be, in its way, as stultifying as a giant one-product factory.

Three, we learn from the mistakes of the last two centuries and insist that our answers always match our questions, and that the distinction between theory and religious belief be maintained.

DAVID BERREBY'S writing about science and culture has appeared in The New York Times Magazine, The New Republic, Slate, The Sciences and many other publications.