MEDICINE AND PHILOSOPHY IN CLASSICAL ANTIQUITY

Aristotle on sleep and dreams 197

also recognises that even medicine may contribute to the study of na-

ture (a fact he hardly could ignore, given the large amount of anatomi-

cal and physiological information preserved in the Hippocratic writings).

This explains his readiness to incorporate medical views into his own

writings.

Having considered his theoretical position on the relationship between

medicine and the study of nature, let us now turn to the practice of the

‘inquisitive non-specialist’ Aristotle in his discussion of the prognostic value

of dreams. For although the distinguished doctors’ opinion is a reputable

view and as such an important indication that there are, in fact, dreams

which play the part of signs of bodily events, the rational justification

(eulogon) for the natural scientist’s sharing this view does not lie in the

doctors’ authority, but in the fact that he can give an explanation for it.

The explanation which follows makes use of empirical claims but is also

based on Aristotle’s own theory of dreams.

For the fact is that movements occurring in the daytime, if they are not very great

and powerful, escape our notice in comparison with greater movements occurring

in the waking state. But in sleep the opposite happens: then it is even the case

that small movements appear to be great. This is evident from what often happens

during sleep: people think that it is lightning and thundering, when there are only

faint sounds in their ears, and that they are enjoying honey and sweet flavours

when a tiny bit of phlegm is running down their throats, and that they go through

a fire and are tremendously hot when a little warmth is occurring around certain

parts of the body. But when they wake up, they plainly recognise that these things
are of this nature. Consequently, since of all things the beginnings are small, it is

evident that also of diseases and of other affections which are going to occur in the

body, the beginnings are small. It is obvious, then, that these are necessarily more

clearly visible in sleep than in the waking state. (Div. somn. 463 a 7 – 21 )

It would seem that Aristotle’s account perfectly meets his requirements for

the dream being a sign of the event, that is, the disease. We have a starting-

point (e.g. a physical disturbance which causes pain) which is going to

produce a disease in the future and which also, at present, causes a dream

image. If the dream is correctly interpreted, it can be reduced to its cause,

which can be recognised as the cause of an imminent disease. Aristotle pays

no attention to the rules for such a correct interpretation of dreams; he

only analyses the causal structure of the relationship between the dream

and the event foreseen in it. This analysis is based on two principles. The

first is one of the corner stones of his theory of dreams as set out inOn

Dreams( 460 b 28 ff.), namely that small movements become manifest more

clearly in sleep than in waking; this is because in the waking state these