Darwin's Beliefs About Dreaming in Humans

The beginnings of modern thought on sleep and dreaming can be traced to the late eighteenth century, the time of the Enlightenment. Scientific writings were read widely by educated people, unlike today, when we are divided into two cultures by the inaccessibility of science to non-experts. In 1794 Erasmus Darwin published Zoonomia, which was partly a medical textbook, partly a treatise on biology. Together with his other writings, its profound influence on the Romantic poets illustrates the depth to which scientific ideas that today might remain obscure swiftly penetrated literary and artistic thinking (King-Hele, 1950). His chapters on sleep and reverie, for instance, informed the development of Coleridge's ideas about dramatic illusion, and his evolutionist ideas found expression in Wordsworth's ode 'Intimations of Immortality from Recollections of early Childhood':

Though inland far we be,

Our souls have sight of that immortal sea

Which brought us hither.

Darwin's analysis of the state of consciousness during dreaming is still well worth reading. It was of course self-evident to him as a rationalist that dreams are a product of the imagination, rather than any mystical intervention. The idea prevalent during the 1960s that lack of dreaming might cause madness was anticipated by two hundred years in Darwin's writing. His view was that dreams prevent delirium by allowing trains of ideas to continue in the absence of sensory input:

if they were to be suspended in sleep like the voluntary motions (which are exerted only by intervals during our waking hours) an accumulation of sensorial power would follow; and on our awakening a delirium would supervene, since these ideas caused by sensation would be produced with such energy, that we should mistake the trains of imagination for ideas excited by irritation; as perpetually happens to people debilitated by fevers on their first wakening; for in these fevers with debility the general quantity of irritation being diminished, that of sensation is increased.

This argument differs from the more modern notion that dreaming is involved in the resolution of conflicts, but similarly ascribes an importance to dreams in preserving sanity.

Central to Darwin's description of dreaming is the suspension of volition, 'and in respect to the mind, we never exercise our reason or recollection in dreams; we may sometimes seem distracted between contending passions, but we never compare their objects, or deliberate about the acquisition of these objects'. This observation, that we remain uncritical observers when dreaming, is an important part of more recent theorizing about dreaming by the psycho physiologist Allan Rechtschaffen, who has described dreams as being 'isolated' and even 'un-imaginative' in the sense that we cannot imagine something else during the action of a dream.

Darwin's work shows just how little scientific thought on dreaming has changed over the intervening centuries, and its popularity and deep influence during his lifetime ensured that these rationalist ideas became an accepted part publicity may have got through, although this issue may have been confounded with ideas of brainwashing and the effects of total sleep loss.