Dreaming | Aristotle 'On Dreams'

On Dreams (De insomniis) is a text, written in 350 BC, by Ancient Greek Philosopher, Aristotle (384 - 322 BC) which is part of his Parva Naturalia - a 'short treatise on nature'. 

In his early years, Aristotle maintained the Platonic belief that the body and soul were separate entities, but subsequently moved on to form a non-dualistic theory that the body and soul (this being a term incorporating the personal consciousness, memories, and experiences) were polarities of the same thing. To put it simply, he adopted the monist view that the physical body - and specifically the brain and soul or consciousness are the one and the same and do not exist separate from one another. 

In his On the Soul (De Anima) treatise, also written in 350 BC, he defined the soul in terms of animating the corporeal body, and giving it life. The soul directs the growth and survival of the physical body, and can be seen as the 'blueprint' for the physical body, giving it purpose and motivation. Therefore, the body and soul - or body and mind in this non-dualistic relationship, exist in dynamic symbiosis.

On Dreams has 3 sections; in the first section, or chapter, Aristotle attempts to determine whether dreams 'pertain to the faculty of thought and intelligence, or that of sense-perception' (De Somno et Vigilia - On Sleep and Dreams). In the second section, he considers sleep and the operation of the sensory organs (De Insomnis - On Sleeping and Waking) . In the third section he explains how dreaming occurs, hypothesising that it is a result of the residual movements of the sensory organs, during sleep (De Divinatione Per Somnum - On Divination Through Sleep). 

Aristotle theorised that during sleep, there was a lack of external sensory stimuli, and due to our eyes being closed, we perceive nothing visually. Comparing the experience of hallucinations to dreaming, he proposed that 'the faculty by which, in waking hours, we are subject to illusion when affected by disease, is identical with that which produces illusory effects in sleep'.

We may misinterpret sensory input when in waking reality (by mishearing something, for example), but this is due to a mistake in reasoning. But generally, our waking perception we only see or hear something incorrectly when we actually see or hear something, and perceive it incorrectly. When asleep, we do not perceive sensory input in the same way, which according to Aristotle, leads to the conclusion that sense and must also be affected in some way. 

Aristotle viewed imagination as what happens when sensory and subjective perception occur after the withdrawal of the external sensory stimuli of waking reality. He recognised that the mind can create realistic 'impressions' or 'afterimages' of things it has experienced in waking reality - a form of visual memory. He believed that during sleep, this effect continues, and is applied to the world of dreaming. When we are awake we are able to easily distinguish between a real, external and imaginary, remembered object - however, in sleep this ability to distinguish is diminished or absent. This is what he thought led to our profound belief in the reality of our dreams. 

In stating that dreams must result from residual movements of the sensory organs, Aristotle also asserted that indigestion might also be a cause for dreams. He claimed:

'We must suppose that, like the little eddies which are formed in rivers, so the movements are each a continuous process, often remaining like what they were when first started, but often, too, broken, into other forms by collisions with obstacles. This gives the reason why no dreams occur in sleep after meals, or to sleepers who are extremely young, e.g., to infants. The movement in such cases is excessive, owing to the heat generated from the food. Hence, just as in a liquid, if one vehemently disturbs it, sometimes no reflected image appears, while at other times one appears, indeed, but utterly distorted, so as to seem quite unlike its original; while, when once the motion has ceased, the reflected images are clear and plain; in the same manner during sleep the images, or residuary images are clear and plain; in the same manner during sleep the images, or residuary movements, which are based upon the sensory impressions, become sometimes quite obliterated by the above described motion when too violent; while at other times the sights are indeed seen, but confused and weird, and the dreams are incoherent, like those of persons who are atrabilious, or feverish, or intoxicated with wine. For all such affections, being spirituous, cause much commotion and disturbance.'

Aristotle's theory of dreaming was therefore one of the first systematic attempts at explaining dreaming, focusing not on mystical, spiritual or supernatural factors, but rather the product of our experience of waking reality which are manipulated by our imagination during sleep. As our logical, rational, fact-checking part of the brain is inactive during sleep, we do not question our perceptions within the dream and accept it as reality.

Aristotle also made explicit reference to lucid dreaming, where the dreamer is consciously aware that he is dreaming - 'often when one is asleep, there is something in consciousness which declares that what then presents itself is but a dream'. Of course the practice of lucid dreaming had already been documented in Ancient Buddhist scriptures, dating back from centuries before Aristotle's contributions.

Aristotle's short theory of dreaming left a continuing legacy in the study of dreams, up until the modern period. In the 17th century, Philosopher, Thomas Hobbes (1588 - 1679) largely adopted the Aristotelian theory of dreams, in particular the idea that dreams occur due to residual sensory organ movement and are products of the imagination. Hobbes argued that dreams are caused by 'the distemper of some inward parts of the Body'. Through this theory, he hoped to better understand the nature of certain types of dreams, for example nightmares. Sigmund Freud (1856 - 1939) stated in The Interpretation of Dreams (1899) that dreams 'do not arise from supernatural manifestations but from the laws of the human spirit' and affirms Aristotle's theory that dreams were the 'mental activity of the sleeper in so far as he is asleep'.