172 Aristotle and his school
also in philosophers like Democritus and, perhaps, Heraclitus, in which
sleep was viewed positively as a state in which humans, or at least some of
us, are capable of modes of cognition not open to us in the waking state
and in which we enjoy a special receptivity to experiences, impulses or, as
Aristotle would put it, ‘movements’ (kin ̄eseis) that we do not receive, or at
least are not aware of, during the waking state; and there are elements of this
in Aristotle’s theory too. These experiences and impulses can be subdivided
into stimuli that have their origin within the dreamer and those that come
from outside.^9 The internal stimuli are the ones arising from the dreamer’s
body, or from his/her internal experiences, memories, thoughts, imagina-
tions or emotions; and these are the stimuli that were of particular interest
to medical writers, such as the author of the Hippocratic workOn Regimen
just mentioned, and to philosophers (like Aristotle) interested in the rela-
tion between the psychological and the physiological aspects of sleep. The
external stimuli can in their turn be subdivided into two categories: those
that have their origin in the natural world, and those that come from the
supernatural (gods, demons, etc.);^10 and this group of external stimuli was
of particular interest to thinkers such as Democritus (and, again, Aristotle)
trying to find an explanation for the phenomenon of prophecy in sleep
concerning events that lie beyond the dreamer’s direct experience.
A similar, related ambivalence surrounded the question whether the
sleeping life of an individual presents a complete negation of the character
and personality of his/her waking life, or whether there is some connection
or continuity between the two states. It would seem that if one defines
sleep negatively (as Aristotle does) as an incapacitation of our powers of
consciousness, the consequence would be that in the sleeping state the
characteristics of our individual personalities are somehow inactivated: it
would be as if, in sleep, we lose our identity and temporarily become like a
plant. Yet, paradoxically, this negative view also allowed a positive valuation
of the state of sleep. For it can be argued that in sleep our souls or minds
are released from our bodies (and from experiences associated with the
body, such as perception and emotion) and acquire a temporary state of
detachedness and purity, thus anticipating the state of the immortal soul
after its definitive detachment from the body after death. This latter view –
that in sleep the soul is set free from the body and regains its ‘proper
nature’ (idia phusis) – was especially found in Orphic and Pythagorean
thought, with its negative view of the body and its dualistic concept of
the relation between soul and body, and found its expression in stories
(^9) See Aristotle,Insomn. 460 b 29 – 30 ;Div. somn. 463 a 3 – 30 ; 463 b 1 – 2 ; 463 b 22 – 3 ; 464 a 15 – 16.
(^10) SeeOn Regimen 4. 87 ( 6. 640 – 2 L.); cf. Arist.,Somn. vig. 453 b 22 – 4 (but on the interpretation of the
termdaimoniosthere see below, pp. 187 , 191 , and 246 – 7 with n. 30 ).