Volume 9, No. 8 - November 1999
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Modern philosophy is founded in dreams--doubly so, in fact. It was a series of peculiar dream episodes, one of them involving a melon, that convinced the young René Descartes that his vocation was to establish a new philosophy. And it was through his "dream argument" (as it came to be called) that Descartes, in the first of his Meditations, began to make his way to a position of universal doubt--the necessary prelude, as he saw it, to the reconstruction of human knowledge on a secure foundation. Descartes noted that I might think "I am seated by the fire, attired in a dressing-gown...when in fact I am lying undressed in bed."

This Cartesian question--How can I be sure I am not always dreaming?--had earlier occurred to Plato and Cicero. It is one of the now classic philosophical problems about dreams. The other classic problem--Can I be immoral in dreams?--was raised by St. Augustine, who was perplexed that he continued to fornicate in his dreams even after he had renounced such wickedness in his waking life.

Contemporary philosophers have tended to focus on a third question--Do dreams amount to experiences that occur during sleep? This is largely the consequence of Norman Malcolm's book Dreaming, which appeared in 1959. Malcolm, a friend and disciple of Wittgenstein's, made the Wittgensteinian-sounding argument that the notion of remembering a dream is nonsensical, since there is no conceivable way of checking the alleged memory. Therefore, Malcolm concluded, dreams are not experiences had while sleeping but merely the propensity to tell weird stories upon awakening.

These are the questions that philosophers have asked about dreams. The ordinary person has rather different concerns. Why do I dream? he wants to know. What is dreaming for? Do my dreams mean anything?

A speculative answer to these latter questions was proposed by Freud, who held that dreams offered the disguised fulfillment of repressed wishes and that the function of dreaming was to keep our sleep from being disturbed by these troublesome desires. But the first empirical breakthrough in dream science came well after Freud, in 1953. That was when Nathaniel Kleitman--the father of sleep research, who died this past August at the age of 104--discovered REM (rapid eye movement) sleep. For periods totaling about two hours each night, Kleitman found, sleepers make jerky eye movements under their closed eyelids; if they are awakened during these periods, they recall having dreams, whereas if they are awakened during non-REM periods, they do not.

Since the discovery of REM sleep, new evidence has shown that we also dream during much of our non-REM sleep. Non-REM dreams tend to be repetitive and thoughtlike, with little imagery--obsessively returning to the suspicion that you left your Filofax somewhere, for example. If non-REM dreams are like neuroses, REM dreams, with their wild conceits and bizarrely stitched-together plots, are more akin to psychoses. Between these two states, there may not be a single moment of our sleep when we are actually dreamless.

It is hard to resist the notion that any activity that occupies as much of our lives as dreaming does must have some sort of evolutionary rationale. (Do other species dream? Some of them certainly do have sleep cycles like ours. The elephant, curiously, sleeps standing up during non-REM periods and then lies down for REM sleep.)

At the moment, there are two prominent--and conflicting--neurobiological theories that attribute adaptive value to dreaming. The Harvard sleep researcher Allan Hobson has hypothesized that the function of dreaming is to fix recent experiences in long-term memory; in other words, we dream about things worth remembering. Francis Crick and Graeme Michison, by contrast, see dreams as a sort of "brainwashing" process in which overlapping memories are eliminated; that is to say, we dream about things worth forgetting.

The most persuasive evolutionary take on dreaming, however, comes from Owen Flanagan, a philosopher at Duke who also holds a professorship there in the department of neurobiology. In his fascinating new book, Dreaming Souls (Oxford), Flanagan submits that, while sleep is certainly an evolutionary adaptation, and consciousness probably is, too, consciousness during sleep is merely a nonadaptive by-product of the two. "Dreams are the spandrels of sleep," he declares, invoking an evolutionary figure of speech popularized by Stephen Jay Gould and Richard Lewontin.

On the night shift, the brain renews itself by stockpiling fresh supplies of neurotransmitters for the next day. Flanagan believes that pulses from the brain stem, which are designed to get this restorative work going, activate stored images and thoughts more or less at random. The partly shut-down cerebral cortex, designed to process sensory experience by the light of day, then performs the same function with this chaotic input during sleep. The dreams that result, Flanagan argues, are neither dazzlingly poetic, as Nietzsche claimed, nor deeply meaningful and in need of elaborate interpretation, as Freud thought.

Trying not to be too deflationary, Flanagan maintains that dreams nonetheless have some self-expressive value, for the random thoughts activated are our thoughts and the narrative structures are imposed by our minds. Perhaps. Yet as we learn more about the neurobiology of dreaming, it gets harder to disagree with the advice of W.H. Auden:

Should dreams haunt you,
  heed them not,
for all, both sweet and horrid,
are jokes in dubious taste,
too jejune to have truck with.