178 Aristotle and his school
8. Insects buzz ( 456 a 18 ).
9. Some people move and perform various activities in sleep, and some of these
people remember their dreams, though they fail to remember the ‘waking’ acts
they perform in sleep ( 456 a 25 ).
- The blood vessels have their origin in the heart ( 456 b 1 ).
11. Words are spoken by people who are in a state of trance and seemingly dead
( 456 b 16 ).
12. Several narcotics make the head heavy ( 456 b 23 ).
13. Children sleep more than other people ( 457 a 4 ).
In many epileptic patients, epileptic seizure begins in sleep ( 457 a 10 ).
The embryo lies quiet in the womb at first ( 457 a 20 ).
People with inconspicuous veins, dwarfish people, and people with big heads
are inclined to much sleep ( 457 a 20 ).
- People with marked veins do not sleep much; nor do melancholics, who in
spite of eating much remain slight ( 457 a 26 ).
18. The brain is the coldest part of the body ( 457 b 30 ).
- The heart has three chambers ( 458 a 15 ff.).
Yet while some of these claims are interesting as testifying either to Aristotle’s
own observational capacities or to his considerable knowledge of medico-
physiological views on sleeping, as a whole they can hardly be regarded
as impressive for their wide range or systematicity; and in the argument,
most of these empirical claims have at best only a marginal relevance to the
topic of sleep. They are mentioned only in passing, and none are presented
by Aristotle as guiding the investigation inductively to a general theory or
as playing a decisive role in settling potentially controversial issues. Nor
does Aristotle explain how observations that seem to be in conflict with
the theoretical views he has expounded can nevertheless be accommodated
within that theory. Thus, in spite of his definition of sleep as the absence of
sensation, Aristotle on several occasions acknowledges that various things
may occur to us while we are in a state of sleep. This is obviously relevant
for the discussion of dreams and divination in sleep that follows after
On Sleep and Waking; but already inOn Sleep and Wakingwe find certain
anticipations of this idea, for example in 456 a 25 – 9 , where he acknowledges
that people may perform waking acts while asleep on the basis of an ‘image
or sensation’ (nos. 9 and 11 ). And on two occasions, the wording ofOn Sleep
and Wakingseems to open the door to sensations of some kind experienced
in sleep: ‘Activity of sense perception in the strict and unqualified sense
(kuri ̄os kai haplos ̄) is impossible while asleep’ ( 454 b 13 – 14 ), and ‘we have
said that sleep is in some way (tropon tina) the immobilisation of sense
perception’ ( 454 b 26 ). These specifications suggest that more may be at
stake than just an unqualified absence of sensation. Yet how the phenomena
