Aristotle and Cicero: the philosophers who doubted prophetic dreams

Alongside the professional interpreters and the faithful who slept in sanctuaries, the ancient world also knew sceptical voices. Some of the greatest Greek and Roman thinkers asked whether dreams could really foretell the future, and answered with caution or open disbelief. Their arguments, surprisingly modern, show that dream divination was always accompanied by lively critical debate, and that believing in dreams was by no means a foregone attitude among the educated people of antiquity.

Aristotle and the dreams of ordinary people

In the short treatises on natural science known as the Parva naturalia, Aristotle devotes three works to sleep, to dreams and to divination in sleep. In the last of these he tackles the question of prophetic dreams directly. His most famous argument is simple: if dreams were sent by the gods, they would send them to the best and wisest of men, not to just anyone and often to people of little intelligence.

Aristotle does not entirely deny that some dreams may anticipate events. He proposes, however, natural explanations: certain dreams would be signs of bodily processes already under way, perceived in sleep when the senses are less distracted, which is why the most attentive physicians took their patients' dreams into account. Others might be causes, because a night image can prompt someone to act. Many, finally, would be mere coincidences, as happens to anyone who throws the dice often.

Cicero and the two books On Divination

In 44 BC, in the months around the death of Caesar, Cicero wrote the dialogue On Divination, in two books. In the first his brother Quintus speaks, defending divination with arguments from the Stoic tradition and offering many examples of dreams that came true, including Hannibal's and that of the poet Simonides, saved from a shipwreck thanks to a dream.

In the second book Marcus, that is Cicero himself, replies with a close-knit critique. If the gods wished to warn us, he observes, why would they do so with obscure images requiring interpreters, instead of speaking clearly while we are awake? And among the countless nights of all humankind, is it not inevitable that some dream should coincide with reality by chance? Cicero concludes that superstition must be uprooted, while the religion of the forefathers must be preserved.

Other critical voices

Scepticism about dreams had even older roots. Already in Herodotus' Histories the counsellor Artabanus explains to Xerxes that night images usually arise from the thoughts and worries of the day. The philosopher Epicurus and his Latin follower Lucretius, in the poem On the Nature of Things, interpreted dreams as extremely fine images that detach themselves from bodies and strike the mind, with no divine intervention at all.

The physician who wrote the Hippocratic treatise On Regimen, by contrast, studied dreams as clues to the state of the body, separating their medical reading from the divinatory one. These theories are long outdated, but their historical interest lies in the effort to explain dreams through natural causes. The author nonetheless allowed that some dreams might have a divine origin, leaving their judgement to the seers.

These positions did not do away with dream divination, which went on flourishing for centuries. But they created a tradition of critical thought to which medieval and modern authors appealed, and which shows that the ancients already knew how to distinguish between the fascination of a dream and the proof of a prophecy. Augustine himself, centuries later, would take up more than one of Cicero's arguments.