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Aristotle's Theory of ‘Sleep and Dreams’ in the Light of Modern and Contemporary Experimental Research

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ELECTRONIC JOURNAL FOR PHILOSOPHY
ISSN 1211-0442 17/2014
Aristotle’s Theory of ‘Sleep and Dreams’
in the light of Modern and
Contemporary Experimental Research
Christina S. Papachristou
University of Economics
Prague
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
2
Abstract
Aristotle’s naturalistic and rationalistic interpretation of the nature and function of
‘sleep’ (πνος) and ‘dreams’ (νύπνια) is developed out of his concepts of the various
parts (μόρια) or faculties/powers (δυνάμεις) of the soul, and especially the functions
of cognitive process: (a) sense/sensation σθησις), (b) imagination (φαντασία), (c)
memory (μνήμη), and (d) mind/intellect (νος). Sleep “is a sort of privation (στέρησις)
of waking (γρήγορσις)“, and dreams are not metaphysical phenomena.
The purpose of this paper is to provide a new reading of Aristotle’s ‘theory of sleep
and dreams’ through its connection to modern and contemporary research. To be more
specific, through this analysis we shall try to present that many of the Stageirite
philosopher’s observations and ideas on the phenomenon of sleep and dreaming have
been verified by current experimental research (e.g. Psychology, Psychophysiology,
Neurobiology, Cognitive Science etc.).
Keywords: Aristotle, sleep, dreams, waking, biological and psychological phenomena,
experimental research.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
3
Introduction
What is sleep? Why do we sleep? Why do we dream? Who we are when we are
asleep? What is the relation between sleep and dreams? Do dreams have meaning?
From antiquity until today, humans wanted to know what happens during the process
of sleep. They wanted to understand and explain the reason we spend one-third of our
lives in this periodic state of rest or inactivity.
Greeks compared to other ancient populations
1
dealt systematically with sleep and
dream function.
2
The Greeks, according to J. Donald Hughes, respected and paid
attention to their dreams as they believed that: (a) they carried messages sent from the
gods, (b) they predicted the future, (c) they had therapeutic powers, and (d) they were
means of communication with the dead.
3
But besides all these, they attempted to
approach and interpret sleep and dreams in a rational way.
Multiple references and theories of sleep and dreams can be found in the writings
of Ancient Greek epic and lyric poets (e.g. Homer,
4
Hesiod,
5
Pindar
6
), dramatists (e.g.
* A previous draft of the present paper was presented at the “31st International Conference on Ancient
and Medieval Philosophy” organized by the Society for Ancient Greek Philosophy (SAGP) and the Society
for the Study of Islamic Philosophy (SSIPS). October 11 - 13, 2013. Fordham University, Lincoln Center,
New York.
1
The oldest written analysis of dreams comes from ancient Mesopotamia (see Hall 1997, 47 and
Oppenheim 1956, 179-373). The Sumerians (3500-1750 B.C.) were one of the earliest civilizations that
arose in the southern area of Mesopotamia. They left behind the first dream-books dating back to 3100
B.C. The Epic of Gilgamesh is considered to be one of the oldest surviving epic poems in the world,
containing numerous dreams and their interpretations (see Heidel 1963; Tigay 1987; Kovacs 1989).
Furthermore, to the ancient Egyptians dreams were very important. They believed that dreams were
related to the supernatural world. They set up Dream Temples for incubating dreams. “Incubation is the
practice of sleeping in a temple chamber in order to obtain oracular or healing dreams”(Hughes 2000,
10).
2
Holowchak 2002, xv says that “the Greeks used several words for ‘dream’ —ὄναρ (n.), ὄνειρος (m.),
ὄνειρον (n.), ὅραμα (n.), χρηματισμός (m.), ἐνύπνιον (n.), and φάντασμα (n.) and a few terms for
‘interpreter of dreams’ —ὀνειροπόλος (m.), ὀνειρομάντις (f./m.), and ὀνειροκρίτης (m.). Of the words for
‘dream’, ὄνειρος, ὅραμα, χρηματισμός, ἐνύπνιον, and φάντασμα took on specific meanings in at least two
ancient accounts, those of Artemidorus and Macrobius: the first three terms being indicative of types of
prophetic dreams and the final two referring to types of non prophetic dreams...The Latin equivalent to
νειρος is somnium (n.)...Macrobius also gives visio (f.) (=ὅραμα) and oraculum (n.) (=χρηματισμός) as
particular kinds of prophetic dreams, and insomnium (n.) (=ἐνύπνιον) and visum (n.) (=φάντασμα) as
kinds of nonprophetic dreams”.
3
Cf. Hughes 2000, 11.
4
The earliest surviving depiction of dream-interpretation in Greek antiquity is in Homer’s epics (8th
century B.C.). In the Iliad and the Odyssey dreams appear as divine or eidolic (εἴδωλον) figures that come
to the sleepers at the head of their bed and convey to them important information about the future.
Some indicative readings for the Iliad and the Odyssey dreams are the following: Messer 1918; Hundt
1935; Rankin 1962, 617-624; Reid 1973, 33-56; Kessels 1978; Lévy 1982, 23-41; Morris 1983, 39-54; Brillante
1990, 31-46; Μαρωνίτης 1993, 3-22; Πόλκας 1999.
5
In Greek mythology Hypnos, the son of Nyx (goddess of Night) and Erebus (god of Darkness and
Shadow) and twin brother of Thanatos (god of Death), was the god or the personification of Sleep.
Hypnos was often pictured as a young man with wings attached to his head or sprouting from his
shoulders. Cf. Hesiod, Theogonia 211-212 and 761-764.
6
Cf. Pindar, Olympia 13.61-80; Idem., Pythia 4. 158-165, 8. 95-100; Idem., Thren. fr. 131b.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
4
Aeschylus, Sophocles, Euripides),
7
historians (e.g. Herodotus),
8
physicians (e.g.
Hippocrates)
9
and philosophers.
10
The Greek philosophers gave special attention to sleep and dreams. Dreams became
part of philosophic and physiologic (biologic) investigation. Pre-Socratic
philosophers,
11
such as Heraclitus,
12
Alcmaeon,
13
Empedocles,
14
Parmenides,
15
Leucippus
16
and Democritus,
17
proposed naturalistic explanations of the cause of sleep
and the formation of dreams, detaching them from the supernatural, while Pythagoras
supported the divine origin of dreams.
18
In the Platonic dialogues the subject of sleep and dreams occurs quite often.
19
In the
most part dreams are regarded by the philosopher as messages received from the gods.
However, from Politeia (Πολιτεία) onwards both philosophical and scientific interest
in the phenomenon of dreaming appears.
20
In the cosmological discourse Timaeus
7
For the nature, function and psycho-analysis of sleep and dreams in Greek tragedy see especially
Messer 1918, 56-102 and Devereux 1976.
8
In Herodotus (484-425 B.C.), the ‘father of history’, dreams are divided into: (a) message dreams,
and (b) symbolic dreams. Cf. Frisch 1968.
9
Hippocrates (460-375 B.C.) used dreams as a diagnostic and prognostic tool and treatment of
psychological and somatic illness. In other words he regarded dreams as a ‘medical’ tool, and as well
he accepted even the mantic or prophetic character of dreams. Cf. Hippocrates, Regimen IV or Dreams 4
86. 9-19, 4 87. 20-16, 4 88. 1-18. See also Byl 1998, 31-36.
10
For a bibliography on Ancient Greek views on sleep and dreams see: van Lieshout 1980; Marelli
1979-1980, 122-137; Guidorizzi 1988; Byl 1998; Holowchak 2002; Hughes 2000.
11
We know most of their work through fragments and testimonia given by later philosophers,
doxographers, physicians, biographers etc.
12
Heraclitus of Ephesus (535/545-485 B.C.) was probably one of the first philosophers who proposed
a naturalistic explanation of dreams, detaching them from the supernatural. Plutarch, De Superstitione
166c5-8 (DK B89): Ἡράκλειτός φησι, τοῖς ἐγρηγορόσιν ἕνα καὶ κοινὸν κόσμον εἶναι, τῶν δὲ κοιμωμένων
ἕκαστον εἰς ἴδιον ἀποστρέφεσθαι. In this fragment it is described the sleep-world (κόσμος) that it is a
private (ἵδιος) world, because the sleeping person is private in the one common (ἕνας καὶ κοινός) world.
13
See note 52.
14
Empedocles (495-435 B.C.), the Acragantine philosopher, believed that sleep is caused by a partial
cooling of heat in the blood, and fire is separated from the other three elements, namely water, air and
earth. Aëtius, Placita V 24.2 (D. 435): Ἐμπεδοκλῆς τὸν μὲν ὕπνον καταψύξει τοῦ ἐν τῷ αἵματι θερμοῦ
συμμέτρῳ γίνεσθαι τῇ δὲ παντελεῖ θάνατον.
15
Parmenides of Elea (5th century B.C.), followed Empedocles’ view on the sleeping phenomenon,
and said that “sleep…is a cooling”, or in other words the blood is chilled, when sleep comes upon the
body. Tertullian, De Anima 45 (A46b): somnum…Empedocles et Parmenides refrigerationem.
16
Leucippus of Elea, Abdera or Miletus (5th century B.C.), the founder of the atomist theory of matter,
asserted that “sleep occurs to the body when the output of thin [atoms] is more than the inflow of
psychic heat”. Ps-Plutarch, Epitome V 25.3 [= Aëtius, V 25.3]: Λεύκιππος οὐ μόνον σώματος γίνεσθαι, ἀλλ
κράσει τοῦ λεπτομεροῦς πλείονι τῆς ἐκκράσεως τοῦ ψυχικοῦ θερμοῦ, τὸν πλεονασμὸν αἴτιον θανάτου· ταῦτα
δ᾽ εἶναι πάθη σώματος οὐ ψυχῆς.
17
Cf. notes 147 and 148.
18
Cf. note 81.
19
In the Platonic writings, according to van Lieshout 1980, 103-104, we can find 45 references in
which the dream-phenomenon occurs. These references are divided “into 23 passages where the subject
‘dream’ is mentioned in passing (as simile, in a metaphorical sense or as proverbial expression) and
24…passages where the subject is dealt with as the author’s primary or direct matter of interest”.
20
Cf. Plato, Politeia V 476c-d, IX 571c-572c; 574d-576b.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
5
(Τίμαιος) Plato (427-347 B.C.) gives a physiological account of sleep, since he associates
the phenomenon of dreaming to vision.
21
But “the philosophical/scientific study of sleep in Ancient Greece reached its apex
in the writings of Aristotle”.
22
Aristotle’s (384-322 B.C.) most important philosophical
and psychophysical ideas on sleep and dreams are developed in three treatises of the
Aristotelian corpus: (a) De Somno et Vigilia (Περ πνου κα γρηγόρσεως), (b) De
Insomniis (Περ νυπνίων), and (c) De Divinatione per Somnum (Περ τς καθ πνον
Μαντικς).
23
These works are very important, because they contain “the only
systematic account of dreams and of prophecy in sleep that has been transmitted to us
from antiquity”.
24
Taking into account the previous view, the current paper has two aims. The first
and foremost aim is to explore Aristotle’s naturalistic and rationalistic interpretation
of the nature and function of ‘sleep’ (πνος) and ‘dreams’ (νύπνια). The second aim
is to show that the Stageirite philosopher “raised ideas that feature prominently”
25
in
modern and contemporary sleep and dream research.
I. Aristotle’s Theory of Sleep (πνος) and Dreams (νύπνια)
a. A physiological interpretation of sleep (πνος) and waking (γρήγορσις)
Aristotle examines the function of sleep and dreams in relation to the biological and
psychological phenomena.
26
In Chapter 1 of the treatise De Somno et Vigilia the
philosopher asserts that sleep “is a sort of privation (στέρησίς) of waking
(γρηγόρσεως)”.
27
But what does this phrase mean? Sleep, according to Aristotle, is not
21
Plato, Timaeus XVI 45d3-46a4: ἀπελθόντος δὲ εἰς νύκτα τοῦ ξυγγενοῦς πυρὸς ἀποτέτμηται· πρὸς γὰρ
ἀνόμοιον ἐξιν ἀλλοιοῦταί τε αὐτὸ κα κατασβέννυται, ξυμφυὲς οὐκέτι τῷ πλησίον ἀέρι γιγνόμενον, ἅτε πῦρ
οὐκ ἔχοντι. παύεταί τε οὖν ὁρῶν, ἔτι τε ἐπαγωγὸν ὕπνου γίγνεται· σωτηρίαν γὰρ ἣν οἱ θεοὶ τῆς ὄψεως
ἐμηχανήσαντο, τὴν τῶν βλεφάρων φύσιν, ὅταν ταῦτα ξυμμύσῃ, καθείργνυσι τὴν τοῦ πυρὸς ντὸς δύναμιν, ἡ
δὲ διαχεῖ τε καὶ ὁμαλύνει τὰς ντὸς κινήσεις, ὁμαλυνθεισῶν δὲ ἡσυχία γίγνεται, γενομένης δὲ πολλῆς μὲν
ἡσυχίας βραχυόνειρος ὕπνος ἐμπίπτει, καταλειφθεισῶν δέ τινων κινήσεων μειζόνων, οἷαι καὶ ἐν οἵοις ν
τόποις λείπωνται, τοιαῦτα καὶ τοσαῦτα παρέσχοντο ἀφομοιωθέντα ντς ἔξω τε ἐγεργεῖσιν
ἀπομνημονεύματα φαντάσματα. Cf. Holowchak 2002, 28.
22
Cf. Mansfield, Goddard, Moldofsky 2003, 61.
23
For a translation with introduction and commentary of these treatises see: Hammond 1902;
Γρατσιάτος 1912; Tricot 1951; Mugnier 1953; Ross 1955; Hett 1975; van der Eijk 1994; Pigeaud 1995;
Gallop 1996; Dönt 1997; Morel 2000; Repici 2003; Σωτηράκης, Ευσταθίου 2006.
24
Cf. van der Eijk 2005, 170. Miller 1994, 40, notices that “unlike Aristotle, Plato did not write a
sustained essay on dreams, but comments on them, often contradictory, are scattered throughout his
works”.
25
Cf. Mansfield, Goddard, Moldofsky 2003, 58.
26
Indicative bibliography on Aristotle’s treatment on sleep and dreams: Preus 1968, 175-182; Huby
1975, 151-152; Kent Sprague 1977, 230-241; Wijsenbeek-Wijler 1978; Lowe 1978, 279-291; Wiesner 1978,
241-280; Kent Sprague 1985, 323-325; Gallop 1988, 257-290; Cambiano, Repici 1988, 121-135; Woods 1992,
179-188; Holowchak 1996, 405-423; Pigeaud 1995; Hubert 1999, 75-111; van der Eijk 2005, 169-205;
Everson 2007, 502-520.
27
Aristotle, De Somno 1.453b26-27: φαίνεται στέρησίς τις ὕπνος τῆς ἐγρηγόρσεως.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
6
contrary to an animal’s physical nature. Unlike deafness or blindness, sleep is a natural
state of a living organism (human and animal). We could say here that sleep, as it is
described in lines 453b25-26, is a natural state of an organism characterized by reduced
or suspended physiological functions. David Gallop says that “to view sleep as ‘a sort
of privation of waking’ (b26-27) is to regard it as an absence (in this case only
temporary) of a positive condition”.
28
The positive condition is waking (γρήγορσις).
29
The Stageirite philosopher considers sleep (πνος) and waking (γρήγορσις) as
affections (πάθη)
30
that require both body and soul,
31
and belong to the ‘primary sense-
faculty’ or ‘primary sensitive/perceptive part’ (πρτον ασθητικόν),
32
known as
‘common sense’ (κοιν ασθησις or sensus communis).
33
Its role is to discriminate
between the sense or sensible objects/objects of perception σθητά)
34
it is receiving
from the various sense organs, which it then judges and interprets. Also, it is
28
Gallop 1996, 120.
29
Kent Sprague 1977, 234 asks and tries to answer the following question: “Sleep is a privation of
waking, but is waking equally a privation of sleep?...Aristotle’s difficulty appears to be the following:
in terms of matter, form and privation, sleep, as a privation of waking, should not only be potential with
respect to waking, but it should come from waking. On inspection, however, it turns out to come,
instead, from a state even further from waking than sleep itself, the plant-like state ‘analogous to sleep’”.
van der Eijk 2005, 185, argues that “sleep and waking are not absolute opposites: when one of them is
present ‘without qualification’ (haplõs), the other may also be present ‘in a certain way’ (pêi)”.
30
Aristotle in De Anima i 1.403a3 speaks about “the affections of the soul“ (τὰ πάθη τῆς ψυχῆς), that
are caused by the functions of sense-perception (αἰσθάνεσθαι), phantasia (φαντασία), memory (μνήμη),
mind/intellect (νοῦς) and sleep (ὕπνος).
31
According to Aristotle, the soul is the form (μορφή or εἶδος) of the body, while the body is the
matter (λη) of the soul (hylomorphism). The soul is inseparable from the body. The soul and body are
not two separate entities but one composite substance. Based on this view sleep and waking are
psychological states of one and the same subject. “That subject cannot, in the case of sleep and waking,
be either the soul or the body alone“ (Gallop 1996, 121).
32
Aristotle, De Somno 1.454a22-24: ἄμφω γάρ στι τὰ πάθη τατα περὶ αἴσθησιν το πρώτου αἰσθητικοῦ.
33
Idem., De Anima iii 1.425a27-28; De Memoria 1.450a10; De Partibus Animalium iii 686a31-32.
According to Modrak 1989, 68-69, Aristotle calls κοινὴ αἴσθησις “by a variety of names”: In the De
Anima and the De Memoria, Aristotle speaks of a common sense (κοινὴ αἴσθησις); in the De Somno, he
speaks of a common capacity (κοινὴ δύναμις); in the De Sensu, of a nonspecific sense faculty (αἰσθητικὸν
πάντων); and in the De Memoria, of a primary sense faculty (πρῶτον αἰσθητικόν)”.
34
Cf. note 58.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
7
responsible for the functions of imagination/phantasia (φαντασία),
35
memory
(μνήμη),
36
sleep (πνος) and dreams (νύπνια).
The primary sense-faculty is located in the heart region, since the heart (καρδία) is
connected with all the other senses.
37
Aristotle defines sleep (πνος) and waking (γρήγορσις) as follows: Sleep is an
affection (πάθος) of the sensitive part of the soul (ασθητικν μόριον),
38
a sort of
35
Imagination/phantasia (φαντασία) is described by the Stageirite philosopher as: (a) the type of
motion (κίνησις), which is generated by actual perception (αἰσθήσεως τῆς κατ᾽ ἐνέργειαν), (b) the faculty
(δύναμις) by which a phantasma (φάντασμα) is presented to us, while phantasma is the product of
imagination and the causal result of the action of ‘αἴσθημα (sensation or sense impression), (c) the
necessary condition for thinking (νοεῖν), (d) the faculty which is not sense (αἴσθησις), or opinion (δόξα),
or knowledge (ἐπιστήμη), or intellect (νοῦς), and (e) the power of the soul, which is associated with
sense-perception (αἰσθάνεσθαι), memory (μνήμη), thinking (νοεῖν), and dreams (ἐνύπνια). Cf. Aristotle,
De Anima iii 3.429a1-2: φαντασία ἂν εἴη κίνησις ὑπὸ τῆς αἰσθήσεως τῆς κατ᾽ ἐνέργειαν γιγνομένης. Op.
cit. iii 3.428a1-5: εἰ δή ἐστιν φαντασία καθ᾽ ἣν λέγομεν φάντασμά τι ἡμῖν γίγνεσθαι κα μὴ ε τι κατὰ
μεταφορὰν λέγομεν, μία τίς στι τούτων δύναμις ἕξις, καθ᾽ ἣν κρίνομεν κα ἀληθεύομεν ψευδόμεθα.
τοιαῦται δ᾽ εἰσὶν αἴσθησις, δόξα, ἐπιστήμη, νοῦς. Op. cit. iii 3.428a5-6: τι μὲν οὖν οὐκ ἐστιν αἴσθησις, δῆλον
ἐκ τῶνδε. Op. cit. iii 3.428a16-18: λλ μὴν οὐδὲ τῶν ἀεὶ ἀληθευόντων οὐδεμία ἔσται, οἷον ἐπιστήμη νοῦς·
στι γὰρ φαντασία κα ψευδής. Op. cit. iii 3.428a24-28: φανερὸν τοίνυν τι οὐδὲ δόξα μετ᾽ αἰσθήσεως, οὐδὲ
δι αἰσθήσεως, οὐδὲ συμπλοκὴ δόξης κα αἰσθήσεως φαντασία ἂν εἴη, διά τε τατα κα δῆλον τι οὐκ ἄλλου
τινός ἐστιν δόξα, λλ ἐκείνου στὶν οὗ κα αἴσθησις.
36
Memory (μνήμη), according to Aristotle, is a function of the soul that belongs not only to human
beings and those animals that possess opinion (δόξα) or intelligence (φρόνησις), but also to some other
animals that perceive time (χρόνος). Cf. Aristotle, De Memoria 1.449b28-30: δι μετὰ χρόνου πᾶσα μνήμη.
σθ σα χρόνου αἰσθάνεται, τατα μόνα τῶν ζῴων μνημονεύει, κα τούτῳ αἰσθάνεται. Ibid. 1.450a16-19:
δι κα ἑτέροις τισὶν ὑπάρχει τῶν ζῴων, κα οὐ μόνον ἀνθρώποις κα τοῖς ἔχουσι δόξαν φρόνησιν. εἰ δὲ τῶν
νοητικῶν τι μορίων ἦν, οὐκ ἂν ὑπῆρχε πολλοῖς τῶν ἄλλων ζῴων, ἴσως δ᾽ οὐδεν τῶν θνητῶν, πε οὐδὲ νῦν
πᾶσι δι τὸ μὴ πάντα χρόνου αἴσθησιν ἔχειν. Idem., Ethica Nicomachea vii 3.1147b3-5: στε κα δι τοτο τὰ
θηρία οὐκ ἀκρατῇ, τι οὐκ ἔχει καθόλου ὑπόληψιν λλ τῶν καθ᾽ ἕκαστα φαντασίαν κα μνήμην.
Memory is closely connected with imagination/phantasia. It belongs to that part of the soul to which
phantasia belongs. It belongs per se to the primary sensitive/perceptive part of the soul and per accidens
to the thinking part of the soul (De Memoria 1.450a 11-14: δὲ μνήμη, κα τῶν νοητῶν, οὐκ ἄνευ
φαντάσματος ἐστιν· στε το νο μὲν κατὰ συμβεβηκὸς ἂν εἴη, καθ᾽ αὑτὸ δὲ το πρώτου αἰσθητικοῦ,).
Mnemonic images (μνημονεύματα), the objects of memory, arise from phantasmata (φαντάσματα), the
products of phantasia.
37
Aristotle, De Somno 2.456a5-7: πάντα γὰρ τὰ ἔναιμα καρδίαν ἔχει, κα ρχτῆς αἰσθήσεως τῆς
κυρίας ντεῦθέν ἐστιν.
38
Aristotle divides the soul into the following parts (μόρια) or faculties (δυνάμεις):
(a) Nutritive (Θρεπτικόν) or Reproductive (Γεννητικόν). The nutritive faculty/power (θρεπτικὴ
δύναμη) of the soul being the same as the reproductive (γεννητική). It exists in all living beings, including
plants and animals (blooded and bloodless). It does it’s own work better when the animal is asleep than
when it is awake. Cf. Aristotle, De Anima ii 4.416a19-20: πε δ᾽ αὐτὴ δύναμις τῆς ψυχῆς θρεπτικὴ κα
γεννητική. Idem., Ethica Eudemia ii 1.1219b22-23: ἐν τῷ πν γὰρ μᾶλλον ἐνεργεῖ τὸ θρεπτικὸν.
(b) Appetitive (desire, spiritedness, wish) [Ὀρεκτικόν (ἐπιθυμία, θυμός, βούλησις)]. Τhe appetitive
power (ὀρεκτικόν) belongs to everything that has sensation (αἴσθησις), and under appetite (ὄρεξις) we
include desire (ἐπιθυμία), spiritedness (θυμός) and wish (βούλησις). The appetitive faculty is both
rational ( βούλησις, namely wish) and irrational ( ἐπιθυμία κα θυμός, namely desire and
spiritedness). Cf. Aristotle, De Anima ii 3.414b1-2: εἰ δὲ τὸ αἰσθητικόν, κα τ ὀρεκτικόν· ὄρεξις μὲν γὰρ
ἐπιθυμία κα θυμὸς κα βούλησις. Ibid. iii 9.432b3-6: πρὸς δὲ τούτοις τὸ ὀρεκτικόν, κα λόγῳ κα δυνάμει
ἕτερον ἂν δόξειεν εἶναι πάντων. κα ἄτοπον δὴ τοτο διασπᾶν· ἔν τε τῷ λογιστικῷ γὰρ βούλησις γίνεται,
κα ἐν τῷ ἀλόγῳ ἐπιθυμία κα θυμός.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
8
tie/bond (δεσμός) or absence of motion (κινησία) imposed on it.
39
It is a state of
powerlessness, due to excess of waking (γρήγορσις),
40
while waking is the contrary
of sleeping and is defined as the ‘release of sensation’ (λελύσθαι τν ασθησιν) from a
state of potency.
41
Consequently, while sleep on the one hand is a kind of potential
sensation (δυνάμει ασθησις), waking on the other hand is an actual sensation
(νεργεί ασθησις).
Aristotle in lines 454a26-32 of the treatise De Somno stresses that all organs that have
a natural function are incapable of exercising continuously. They become fatigued and
no longer perform their function. For example, if the eyes continue seeing (actual
sensation) beyond their natural time of their functioning period, they become unable
to act. They need some time to calm down and rest (potential sensation).
So, if a living being has sensation (ασθησις),
42
it is impossible to continue
actualizing its powers continuously (νεργεί ασθησις) or, in other words, to be
always awake (γρήγορσις). If time is exceeded during which continuous sensation is
possible, the living being becomes fatigue and needs to sleep (πνος). Sleep, which is
(c) Sensitive (Αἰσθητικόν). The sensitive faculty/power (αἰσθητική) of the soul exists in all animals.
In plants there is no sensitive faculty/power apart from the nutritive. The sensitive part of the soul
cannot exist without the nutritive. Cf. Ibid. ii 3.415a1-3: ἄνευ μὲν γὰρ το θρεπτικοῦ τὸ αἰσθητικὸν οὐκ
ἔστιν· το δ᾽ αἰσθητικοῦ χωρίζεται τὸ θρεπτικὸν ἐν τοῖς φυτοῖς.
(d) Locomotive/Motive according to place (Κινητικὸν κατὰ τόπον). Τhe locomotive faculty/power
(κίνησις κινητικὸν κατὰ τόπον) is related to the local movement of animals and is also described as the
‘progressive motion’ (πορευτικὴ κίνησις). Cf. Ibid. iii 9.432b8-14: τί τὸ κινοῦν κατὰ τόπον τὸ ζῷόν
ἐστιν;…λλ περὶ τῆς κατὰ τόπον κινήσεως, τί τὸ κινοῦν τὸ ζῷον τὴν πορευτικὴν κίνησιν, σκεπτέον.
(e) Imaginative (Φανταστικόν). the imaginative (φανταστικόν) is distinct from the other parts (μόρια)
or faculties (δυνάμεις), and it is difficult to say with which of the parts it is identical or not. Cf. Ibid. iii
9.432a28-432b4: περὶ ὧν κα νῦν εἴρηται, τό τε θρεπτικόν, κα τοῖς φυτοῖς ὑπάρχει κα πᾶσι τοῖς ζῴοις, κα
τὸ αἰσθητικόν, οὔτε ὡς λογον οὔτε ὡς λόγον ἔχον θείη ἄν τις ῥᾳδίως. τι δὲ τὸ φανταστικόν, τῷ μὲν εἶναι
πάντων ἕτερον, τίνι δὲ τούτων ταὐτὸν ἕτερον, ἔχει πολλὴν ἀπορίαν, εἴ τις θήσει κεχωρισμένα μόρια τῆς
ψυχῆς. πρὸς δὲ τούτοις τὸ ὀρεκτικόν, κα λόγῳ κα δυνάμει ἕτερον ἂν δόξειεν εἶναι πάντων.
(f) Rational (Νοητικόν) or Discursive (Διανοητικόν). Species like man have in addition the rational οr
discursive faculty/power of the soul. This faculty of the soul judges truth and falsehood and
apprehends. Cf. Ibid. ii 3.414b16-19: ἐνίοις δὲ πρὸς τούτοις ὑπάρχει κα τὸ κατὰ τόπον κινητικόν, ἑτέροις δὲ
κα τὸ διανοητικόν τε κα νοῦς, οἷον ἀνθρώποις κα εἴ τι τοιοῦτον ἕτερόν ἐστιν κα τιμιώτερον. Cf.
Papachristou 2013, 20-28.
39
Aristotle, De Somno 1.454b10-14: γὰρ ὕπνος πάθος τι το αἰσθητικοῦ μορίου ἐστίν, οἷον δεσμὸς κα
ἀκινησία τις, στ ἀνάγκη πᾶν τ καθεῦδον ἔχειν τὸ αἰσθητικὸν μόριον. αἰσθητικὸν δὲ τὸ δυνατὸν
αἰσθάνεσθαι κατ᾽ ἐνέργειαν.
40
Ibid. 1.454b4-6: εἰ οὖν τὸ τοιοῦτον πάθος ὕπνος, τοτο δ᾽ στὶν ἀδυναμία δι ὑπερβολὴν το ἐγρηγορέναι.
41
Ibid. 1.454a32-454b4: εἰ τοίνυν τὸ ἐγρηγορέναι τούτῳ ὥρισται τῷ λελύσθαι τὴν αἴσθησιν, τῶν δ᾽
ἐναντίων τὸ μὲν ἀνάγκη παρεῖναι τὸ δ᾽ οὔ, τὸ δ᾽ ἐγρηγορέναι τῷ καθεύδειν ἐναντίον, κα ἀναγκαῖον παντὶ
θάτερον ὑπάρχειν, ἀναγκαῖον ἂν εἴη καθεύδειν.
42
Sense/sensation (αἴσθησις) or sense-perception (αἰσθάνεσθαι): The act of perceiving by
sense/sensation (αἴσθησις) is what distinguishes an animal (τὸ ζῷον) from non-animal (τὸ μ ζῷον).
“Sense/sensation is that which is receptive of sensible forms without their matter, just as wax receives
the imprint of a ring without its iron or gold of which it is made” (Aristotle, De Anima ii 12.424a17-19:
μὲν αἴσθησίς στι τὸ δεκτικὸν τῶν αἰσθητῶν εἰδῶν ἂνευ τῆς ὕλης, οἷον κηρὸς το δακτυλίου ἄνευ το
σιδήρου κα το χρυσοῦ δέχεται τὸ σημεῖον).
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
9
the opposite of waking, is essential for the preservation (νεκα δ σωτηρίας) of the
living beings: they have the opportunity to rest (νάπαυσις)
43
(see DIAGRAM 1).
Moreover, during sleep are promoted nutrition and growth.
44
DIAGRAM 1
How does sleep come? What causes sleep? Aristotle describes the physiology of
sleep based on the knowledge of his time. As soon as human beings and animals have
sensation (ασθησις), then they must take food and grow. But, when do they acquire
sensation? The embryos, according to the philosopher, possess only the nutritive
(θρεπτική) soul; they absorb nutriment without sensation; they have in potentiality all
the other parts of the soul, which are actualized later, namely, after birth.
Now, since an animal has sensation, it takes nourishment. Food (τροφή) in its final
form is, in all blooded animals, blood μα), and in bloodless animals something
analogous to blood.
45
When food enters the parts intended for its reception, the
evaporation arising from it, enters into the veins, and there it is transformed into blood,
43
Aristotle, De Somno 3.458a29-32: ἐξ ἀνάγκης μὲν γινόμενος (οὐ γὰρ ἐνδέχεται ζῷον εἶναι μὴ
συμβαινόντων τῶν ἀπεργαζομένων αὐτό), ἕνεκα δὲ σωτηρίας· σώζει γὰρ ἀνάπαυσις.
44
Ibid. 1.454b32-455a3: σημεῖον δ᾽ τι κα τὸ ἔργον τὸ αὑτο ποιεῖ τὸ θρεπτικὸν μόριον ἐν τῷ καθεύδειν
μᾶλλον ἐν τῷ ἐγρηγορέναι· τρέφεται γὰρ κα αὐξάνεται τότε μᾶλλον, ὡς οὐδὲν προσδεόμενα πρὸς τατα
τῆς αἰσθήσεως.
45
Ibid. 3.456a32-456b2: φανερὸν δὴ τι πε ἀναγκαῖον τῷ ζώ, ὅταν αἴσθησιν ἔχῃ, τότε πρῶτον τροφήν
τε λαμβάνειν κα αὔξησιν, τροφὴ δ᾽ στ πᾶσιν ἐσχάτη τοῖς μὲν ἐναίμοις το αἵματος φύσις τοῖς δ᾽ ἀναίμοις
τὸ ἀνάλογον, τόπος δὲ το αἵματος αἱ φλέβες, τούτων δ᾽ ρχ καρδία.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
10
and is carried to the origin of veins and the center of sense-perception (ασθάνεσθαι),
46
namely, the heart.
47
Ιn lines 456b17-19 of De Somno the philosopher stresses once again that sleep is not
an ‘impotence’ (δυναμία) of the sensitive part of the soul. He adds that
“unconsciousness, choking, and swooning produce such an impotence” (κα γρ
κνοια κα πνιγμός τις κα λιποψυχία ποιε τν τοιαύτην δυναμίαν). Instead, sleep
arises from the concentrated hot matter (moist and solid) exhaled (ναθυμίασις) from
ingested food.
48
The exhaled hot matter rises through the circulatory system to the
brain,
49
which is the coldest part of the body,
50
and the seat of sleep.
51
Brain cools hot
matter and makes it flow back in the heart (see DIAGRAM 2). These remarks on the
cause of sleep, strongly suggest that Aristotle is drawing them from Alcmaeon’s
account on sleep.
52
46
Sense-perception (αἰσθάνεσθαι) or the act of perceiving by sense is a form of being affected or
moved (Aristotle, De Anima i 5.410a25-26: τὸ γὰρ αἰσθάνεσθαι πάσχειν τι κα κινεῖσθαι τιθέασιν).
According to Aristotle, when an animal perceives an object (αἰσθητόν), sense-perception (αἰσθάνεσθαι)
takes on the form of the object it perceives. Sense-perception is actualized by the sense quality of the
object. The sense quality, which is a potentiality (δυνάμει) of the object, becomes an actuality (ἐνεργείᾳ)
through the action of the sense organs.
47
Aristotle, De Somno 3.456b3-5: τῆς μὲν οὖν θύραθεν τροφῆς εἰσιούσης εἰς τοὺς δεκτικοὺς τόπους γίνεται
ἀναθυμίασις εἰς τὰς φλέβας, κε δὲ μεταβάλλουσα ἐξαιματοῦται κα πορεύεται ἐπὶ τὴν ἀρχήν.
48
Ibid. 3.456b17-19: οὐκ ἔστιν ὕπνος ἀδυναμία πᾶσα τοῦ αἰσθητικοῦ, λλ ἐκ τῆς περὶ τὴν τροφὴν
ἀναθυμιάσεως γίνεται τὸ πάθος τοῦτο.
49
Ibid. 3.457b20-22: Γίνεται γὰρ ὕπνος, ὥσπερ εἴρηται, τοῦ σωματώδους ἀναφερομένου ὑπὸ το θερμοῦ
δι τῶν φλεβῶν πρὸς τὴν κεφαλήν.
50
Aristotle, De Partibus Animalium ii 7.652a27-28: μὲν γὰρ γκέφαλος ψυχρότατον τῶν ἐν τῷ σώματι
μορίων.
51
Idem., De Somno 3.457b27-29: οὐ μὴν λλ κύριός γ᾽ στν τόπος ὁ περὶ τὸν ἐγκέφαλον. Aristotle’s
theory of the role and function of the brain has not been accepted either by scientists or by philosophers
(e.g. Galen, T. E. Lones, C. G. Gross etc.), all of whom have characterized it as “incorrect” and
“anchronistic”, since, as they point out, the Stageirite philosopher believed that the supreme organ of
the body was the heart and not the brain. Contrary to this view, I believe that “it is to a great extent
unfair to claim that: (a) Aristotle dismissed the role of the brain in the human organism quite as much
as it is often claimed, and (b) the only functions of the brain in the Aristotelian theory of sense-
perception are (i) to cool the heat of the blood generated by the heart, and (ii) to produce sleep”. I have
dealt with this issue in more detail in Papachristou 2008, 9-21.
52
Alcmaeon of Croton (5th century B.C.) was probably the first Pythagorean philosopher and
physician, who proposed “the first rational theory for the cause of sleep” (cf. Thorphy 2005, 14). He said
“sleep occurs from retreat of the blood to the blood vessels, and awakening from bloods flowing back”
[Aëtius, Placita, V, 24, 1 (DK 24 A18): Ἀλκμαίων ἀναχωρήσει το αἵματος εἰς τὰς αἱμόρρους φλέβας ὕπνον
γίνεσθαί φησι, τὴν δὲ ἐξέγερσιν διάχυσιν, τὴν δὲ παντελῆ ἀναχώρησιν θάνατον].
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
11
DIAGRAM 2
Aristotle adds and some other things that induce sleep:
Narcotics (πνωτικά), whether liquid or solid, like opium poppy (Papaver
somniferum), mandrake (Mandragora officinarum), wine (an alcoholic beverage),
bearded-darnel (Lolium tementulum) make the head heavy:
σημεον δ τούτων κα τ πνωτικά· πάντα γρ καρηβαρίαν ποιε, κα τ ποτ κα
τ βρωτά, μήκων, μανδραγόρας, ονος, αραι (De Somno 3.456b29-31)
Some states of fatigue (κόπος):
μν γρ κόπος συντηκτικόν, τ δ σύντηγμα γίνεται σπερ τροφ πεπτος, ν μ
ψυχρν (Op. cit. 3.456b35-457a1)
Certain diseases (νόσοι) “with an excessive amount of moist and hot, as
happens with fever-patients and the cases of lethargy”:
κα νόσοι δέ τινες τατ τοτο ποιοσιν, σαι π περιττώματος γρο κα θερμο,
οον συμβαίνει τος πυρέττουσι κα ν τος ληθάργοις (Op. cit. 3.457a1-3)
Moreover, young children, people with small veins, dwarfs and people with large
heads, sleep a lot:
τι δ πρώτη λικία· τ γρ παιδία καθεύδει σφόδρα δι τ τν τροφν νω
φέρεσθαι πσαν. σημεον δ τ περβάλλειν τ μέγεθος τν νω πρς τ κάτω
κατ τν πρώτην λικίαν, δι τ π τατα γίνεσθαι τν αξησιν. (Op. cit.
3.457a3-7)
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
12
Further, early childhood has this effect; for children sleep very much, because all
their food rises upwards. A proof of this whereof seems in the excessive size of the
upper parts compared with the lower during early childhood, because growth takes
place in these parts.
κα τ λον δ φίλυπνοι ο δηλόφλεβοι κα ο νανώδεις κα ο μεγαλοκέφαλοι·
τν μν γρ α φλέβες στεναί, στ ο ῥᾴδιον διαρρεν κατιν τ γρόν, τος δ
νανώδεσι κα μεγαλοκεφάλοις νω ρμ πολλ κα ναθυμίασις. (Op. cit.
3.457a21-25)
Also, in general, people with small veins, dwarfs and those with large heads are
fond of sleeping; for in the former the veins are narrow, so that the moisture cannot
easily flow through them, while for dwarfs and those with large heads the upward
surge of exhalation is great.
Then, we have the question: When does awakening occur? Aristotle says that
awakening occurs when digestion is completed. When the great amount of heat, which
is concentrated from the surrounding parts of the body has taken control, and the
thickest blood has been separated from the purest blood. The thinnest and purest
blood is in the head, the thickest and most troubled in the lower parts:
γείρεται δ, ταν πεφθ κα κρατήσ συνεωσμένη θερμότης ν λίγ πολλ κ
το περιεσττος, κα διακριθ τό τε σωματωδέστερον αμα κα τ καθαρώτατον, στι
δ λεπτότατον μν αμα κα καθαρώτατον τ ν τ κεφαλ, παχύτατον δ κα
θολερώτατον τ ν τος κάτω μέρεσιν. (Op. cit. 3.458a10-15)
Let us finish this section with a brief “explanation of sleep in terms of Aristotle’s
doctrine of ‘four causes’ [ατια]”.
53
(a) The material cause or material substratuum of sleep (De Somno 3.457a33-b3) =
causa materialis is, according to Ross, the hot matter exhaled from ingested food.
54
53
Gallop 1996, 126. Aristotelian commentators are puzzled about whether Aristotle applied the
doctrine of ‘four causes’ to his explanation of sleep. Woods 1992, 180-181, asserts that “it seems mistaken
to suppose that at 455b13-15, we have an undertaking by Aristotle to consider all four causes in relation
to sleep; so the failure to deal with the formal and material (explicitly at least) in the subsequent text
does not call for explanation. The four causes are mentioned, in typical Aristotelian fashion, so as to
relate the discussion to Aristotle’s general methodological frameworks”. See also Gallop 1996, 127-128,
who notices that “the ‘formal’ and ‘material’ causes are nowhere to be found” and it is doubtful whether
Aristotle explains “sleep in terms of his ‘four cause’ schema”.
54
Aristotle, De Somno 3.457a33-b3: Ὥστε φανερὸν ἐκ τῶν εἰρημένων ὅτι ὕπνος ἐστ σύνοδός τις τοῦ
θερμοῦ εἴσω καὶ ἀντιπερίστασις φυσικ δι τὴν εἰρημένην αἰτίαν. Ross 1955, 260, believes that Aristotle
considers all ‘four causes’ in relation to sleep. The philosopher deals with: (a) the material cause in
457a33-b1, (b) the final cause in 455b16-28 and 458a29-30, (c) the efficient cause in 455b28 ff. and 456a30-
458a25, and (d) the formal cause in 458a30-32. Cf. van der Eijk 2005, 177. Also, Mansfield, Goddard and
Moldofsky 2003, 60, regard that the Stageirite applies the four fundamental causes to his study of sleep,
and they locate the ‘material causes’ of sleep to “the matter that is digested, the heart, the veins, and
possibly the brain”.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
13
(b) The cause of sleeping (τί μν ον τ ατιον το καθεύδειν, De Somno 3.458a25-26)
= τ τί ν εναι or causa efficiens “is the reverse flow of the solid matter, carried
upwards by the naturally inherent heat, en masse towards the primary sense-organ”.
55
(c) What is sleep (κα τί στιν πνος, op. cit. 3.458a28)? = μορφή or causa formalis
sleep is the inhibition of the primary sense-organ, rendering it incapable for
functioning.
56
(d) The final cause of sleeping (ξ νάγκης μν γινόμενος, op. cit. 3.458a29-30) =
τέλος or causa finalis sleep is for the sake of animal preservation, since rest
preserves.
57
b. The formation of dreams (νύπνια)
In the treatise De Insomniis (Περ νυπνίων) Aristotle examines dreams (νύπνια)
and inquires to which part (μόριον) or faculty (δύναμις) of the soul they occur.
Μετ δ τατα περ νυπνίου ζητητέον, κα πρτον τίνι τν τς ψυχς φαίνεται, κα
πότερον το νοητικο τ πάθος στ τοτο το ασθητικο. (De Insomniis 1.458a33-
458b2)
The Macedonian philosopher argues that sense/sensible objects σθητά),
58
namely the objects of perception, produce sensation σθησις) in the sense organs. The
affection (πάθος) produced by them, specifically ασθημα [“the causal result of the
action of ‘ασθητόν’ (object of perception)”],
59
persists in the sense organs not only
while the senses are in actuality, but also after ασθητά have gone.
60
It occurs not only
during the waking state, but also when sleep takes place.
The affection (πάθος) that persists when the sense organs are no longer active seems,
for Aristotle, to be similar to that observed in the case of objects moving in space (π
τν φερομένων οικεν εναι). Because in the case of these objects movement continues,
both in the air and in the water, even when the moving agent is no longer in contact
with them. In addition, the philosopher points out that something like this takes place
also in the case of alteration or qualitative change (λλοίωσις). What is warmed by a
hot object, warms what it is adjacent to it, and the transmission is continuous, until the
55
Gallop 1996, 83.
56
Aristotle, De Somno 3.458a28-30: κα τί ἐστιν ὁ ὕπνος, ὅτι τοῦ πρώτου αἰσθητηρίου κατάληψις πρὸς τὸ
μὴ δύνασθαι ἐνεργεῖν.
57
Ibid. 3.458a30-32.
58
Aristotle, De Anima ii 6.418a8-11: λέγεται δὲ τὸ αἰσθητὸν τριχῶς. ὧν δύο μὲν καθ᾽ αὑτά φαμεν
αἰσθάνεσθαι, τὸ δὲ ἓν κατὰ συμβεβηκός. τῶν δὲ δύο τὸ μὲν ἴδιόν ἐστιν ἑκάστης αἰσθήσεως, τὸ δὲ κοινὸν
πασῶν. The Stageirite distinguishes three kinds of sensible objects (αἰσθητά): (a) per se (καθ᾽ αὑτά), (b)
per accidens (κατὰ συμβεβηκός) and (c) common (κοινά).
59
Wedin 1988, 37. Wedin 1988, 37, translates ‘αἴσθημα’ as ‘perceptual state’ and Sorabji 2004, 82, as
‘sense-image’.
60
De Insomniis 2.459a25-28: τὰ γὰρ αἰσθητὰ καθ᾽ ἕκαστον αἰσθητήριον ἡμῖν ἐμποιοῦσιν αἴσθησιν, κα τὸ
γινόμενον ὑπ᾽ αὐτῶν πάθος οὐ μόνον ἐνυπάρχει ἐν τοῖς αἰσθητηρίοις ἐνεργουσῶν τῶν αἰσθήσεων, αλλὰ κα
ἀπελθουσῶν.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
14
starting-point is reached.
61
The previous examples that are classic cases of the ‘domino
effect’ “provide a model for understanding what occurs in perception more
generally”.
62
The sensory impulses/sensory movements (κινήσεις) arising from ασθήματα are
present during the waking and sleeping state. These sensory impulses are compared
with those of flowing rivers.
63
For in the daytime, while the senses (ασθήσεις) and the
mind/thought (διάνοια) are in actuality (νεργοσαι), sensory impulses are pushed
away. At night, while the special senses are inactive, because of the reverse flow of
heat from the outer parts to the interior, these sensory impulses are carried through
blood to the seat of senseperception, the heart, and become evident, as the
disturbance subsides.
64
Thus, dreams (νύπνια) originate from the preserved
(σωζόμενη) movement of sensory impulses in the sense organs “from the moment of
their arrival (in the waking state) to the moment of their transport to the heart”.
65
The phenomenon that is called dreaming (νυπνιάζειν) does not belong to:
66
(a) What judges (δοξάζον): opinion/judgement (δόξα) is defined as “one of the
faculties or habits, by which we judge, and put us in truth or falsity”.
67
It follows
sensation σθησις) and should be impossible in dreaming. During sleep, says the
Aristotelian commentator Michael Ephesius, opinion, just as sensation, is disabled
from exercising its function:
δόξα νευ ασθήσεως οχ πολαμβάνει, δ ασθησις ν τος πνοις οκ νεργε,
οκ ν εη οδ τς δόξης τ νύπνιον πάθος). (Michael Ephesius, Parva Naturalia
Commentaria 22.1.61.23-25)
(b) What thinks (διανοούμενον): thought (διάνοια) is the cognitive process that
results in belief and knowledge.
It is clear, from (a) and (b), that dreaming does not belong to the rational (νοητικόν)
or the discursive (διανοητικόν) part (μόριον) or faculty (δύναμις) of the soul. In other
61
Op. cit. 2.459a25-459b4: τὰ γὰρ αἰσθητὰ καθ᾽ ἕκαστον αἰσθητήριον ἡμῖν ἐμποιοῦσιν αἴσθησιν͵ κα τὸ
γινόμενον π΄ αὐτῶν πάθος οὐ μόνον ἐνυπάρχει ἐν τοῖς αἰσθητηρίοις ἐνεργουσῶν τῶν αἰσθήσεων͵ λλ κα
ἀπελθουσῶν. Παραπλήσιον γὰρ τὸ πάθος ἐπί τε τούτων κα ἐπὶ τῶν φερομένων ἔοικεν εἶναι. κα γὰρ ἐπὶ τῶν
φερομένων το κινήσαντος οὐκέτι θιγγάνοντος κινεῖται· τὸ γὰρ κινῆσαν ἐκίνησεν ἀέρα τινά͵ κα πάλιν οὗτος
κινούμενος ἕτερον. κα τοῦτον δὴ τὸν τρόπον͵ ως ἂν στῇ͵ ποιεῖται τὴν κίνησιν κα ἐν ἀέρι κα ἐν τοῖς ὑγροῖς.
μοίως δὑπολαβεῖν τοτο δε κα ἐπ᾽ λλοιώσεως· τὸ γὰρ θερμανθὲν ὑπὸ το θερμοῦ τὸ πλησίον θερμαίνει,
κα τοτο διαδίδωσιν ως τῆς ρχῆς.
62
Gallop 1996, 145.
63
De Insomniis 3.461a8-25.
64
Op. cit. 3.460b28-461b8.
65
van der Eijk 2005, 183.
66
De Insomniis 1.459a8-11: Ὅτι μὲν οὖν οὐκ ἔστι τοῦ δοξάζοντος οὐδὲ το διανοουμένου τὸ πάθος τοῦτο
καλοῦμεν ἐνυπνιάζειν, φανερόν. ἀλλ οὐδὲ το αἰσθανομένου ἁπλῶς· ὁρᾶν γὰρ ν ἦν καὶ ἀκούειν ἁπλῶς.
67
De Anima iii 3.428a3-4: μία τίς ἐστι τούτων δύναμις ἢ ἕξις, καθ᾽ ἣν κρίνομεν καὶ ἀληθεύομεν ἢ
ψευδόμεθα.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
15
words it means that we should not be able to think during the sleeping state. Whereas,
in lines 459a6-8 and 462a29-30, Aristotle, as van der Eijk remarks, “speak[s] of an
activity of ‘judgement’ (doxa) and of the presence of ‘true thoughts’ (alêtheis ennoiai) in
sleep, but it remains vague”:
68
κα τ μν δόξα λέγει τι ψεδος τ ρώμενον, σπερ γρηγορόσιν, τ δ
κατέχεται κα κολουθε τ φαντάσματι. (De Insomniis 1.459a6-8)
and sometimes opinion/judgement says that what is seen is as falsehood, just as in
the waking state, and at other times [opinion] is held in check and follows the phantasm.
οδ, σαι δ ν τ πν γίνονται ληθες ννοιαι παρ τ φαντάσματα. (Op. cit.
3.462a29-30)
neither can those true thoughts which occur in sleep, over and above the
phantasmata (Op. cit. 3.462a29-30)
69
(c) What perceives (ασθανόμενον) in an unqualified sense (πλς): For then it
would be possible in a dream to see and hear in an unqualified sense (πλς). But in
sleep both the particular senses and their primary sense-faculty/common sense are
inactivated, and for this reason dreams are illusory
70
and “do not give us faithful
images of reality”.
71
Aristotle believes that a dream (νύπνιον) is a kind of phantasma (φάντασμα)
phantasma is the product of phantasia, i.e., a kind of (mental) representation/image
72
that occurs in sleep.
73
Also, he notices that the imaginative (φανταστικόν) is the same
as the sensitive σθητικόν) part (μόριον) of the soul, although they are different in
their being ναι).
74
Therefore, νυπνιάζειν “is an activity of the sensitive part, but
belongs to it qua imaginative” (see DIAGRAM 3).
75
68
van der Eijk 2005, 176.
69
De Insomniis 3.462a29-30: οὐδ, ὅσαι δὴ ἐν τῷ πν γίνονται ἀληθεῖς ἔννοιαι παρὰ τὰ φαντάσματα.
70
Op. cit. 1.458b26-28: Δῆλον δὲ περὶ τούτων ἁπάντων τό γε τοσοῦτον, τι τῷ αὐτῷ κα ἐγρηγορότες ἐν
ταῖς νόσοις ἀπατώμεθα, τι τοῦτ᾽ αὐτὸ κα ἐν τῷ πν ποιεῖ τὸ πάθος.
71
See Hughes 2000, 16.
72
For the interpretation of the word phantasma (φάντασμα), see Papachristou 2013, 32: “My
suggestion is that the word φάντασμα, which is mentioned twelve times in De Anima (also thirteen
times in De Memoria, thirteen in De Insomniis, four in De Divinatione, two in De Somno, two in Metaphysica,
one in Ethica Nicomachea, one in Protrepticus) may conveniently and aptly be translated as: (a)
‘representation’ or ‘image’ in contexts where φάντασμα is related only with the faculty of phantasia (e.g.
εἰ δή ἐστιν φαντασία καθ᾽ ἣν λέγομεν φάντασμά τι ἡμῖν γίγνεσθαι, De Anima iii 3.428a1-2), and (b) as
‘mental representation’ or ‘mental image’, when φάντασμα is described by the philosopher as the
substratum upon which the mind works [e.g. (δι οὐδέποτε νοεῖ ἄνευ φαντάσματος ψυχή), De Anima iii
7.431a16-17]”.
73
De Insomniis 3.462a15-16: Ἐκ δὴ τούτων ἁπάντων δεῖ συλλογίσασθαι ὅτι ἐστ τὸ ἐνύπνιον φάντασμα
μέν τι καὶ ν πν.
74
Op. cit. 1.459a15-17: πε δὲ περὶ φαντασίας ἐν τοῖς περὶ ψυχῆς εἴρηται, κα στι μὲν τὸ αὐτὸ τῷ
αἰσθητικῷ τὸ φανταστικόν, τὸ δ᾽ εἶναι φανταστικῷ κα αἰσθητικῷ ἕτερον.
75
Op. cit. 1.459a21-22: φανερὸν τι το αἰσθητικοῦ μέν στι τὸ ἐνυπνιάζειν, τούτου δ᾽ τὸ φανταστικόν.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
16
At this point we can pose the question: What is the difference between a dream
(νύπνιον) and a phantasma (φάντασμα)? Themistius (Sophonias),
76
the Aristotelian
commentator, gives an answer to the previous question. νύπνιον is that kind of
dream in which you don’t know at that time that you are dreaming. Whereas
φάντασμα is a kind of dream in which you become aware at that time that you are
dreaming:
οκ ε δ, π μέντοι τς δόξης ε δοξάζομεν συναισθανόμεθα τι δοξάζομεν. οκ
ρα οδ οτω δόξης τ νύπνια. μα δ δλον ς ο πν τ ν πν φάντασμα
νύπνιόν στιν, λλ ταν μέν τι ρν τις μ ννο, τι περ ρ ναρ στίν, νύπνιον
τοτο γε· ταν δ ρν δύνηται ννοεν τι τ ρώμενον νύπνιόν στιν, δη τοτο
φάντασμα, νύπνιον δ οδαμς. [Themistius (Sophonias), Parva Naturalia
Commentarium 5.6.30.3-8]
At the end of the treatise De Insomniis the philosopher notices that dreams (νύπνια)
do not occur to very young children (οδ τος παιδίοις γίνεται νύπνιον) and
immediately after the intake of food (οδ μετ τν τροφν καθυπνώσασιν). He also
mentions that there are people who have never dreamt in their whole lives (τισι
συμβέβηκεν στε μηδν νύπνιον ωρακέναι κατ τν βίον),
77
and others who were
late dreamers, namely, they have observed them late in life (νίοις δ κα προελθοσι
πόρρω τς λικίας γένετο).
78
76
The Paraphrase of parts of Aristotle’s Parva Naturalia should not be attributed to Themistius but to
Sophonias (see Wendland 1903, v-x).
77
Sorabji 2004, 36, stresses that “we could assume that Aristotle’s supposed non-dreamers had
simply not remembered their dreams. Indeed, Aristotle himself once mentions this possibility (453b18-
20), though it is not explicitly pursued further”.
78
De Insomniis 3.462a31-b11. See also Historia Animalium, iv 10.537b16-20.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
17
DIAGRAM 3
c. Dreams (νύπνια) are not divine. Dreams may be signs τια), causes
(σημεα) or coincidences (συμπτώματα).
Aristotle in his treatise De Divinatione per Somnum (Περ τς καθ πνον Μαντικς)
acknowledges that dreams sometimes foretell the future, and rejects the popular belief
of the divinatory power of dreams. He argues that some other animals than man dream
(κα τν λλων ζων νειρώττει), and ordinary people (ετελες νθρωποι) experience
prophetic dreams:
λως δ πε κα τν λλων ζων νειρώττει τινά, θεόπεμπτα μν οκ ν εη τ
νύπνια, οδ γέγονε τούτου χάριν, δαιμόνια μέντοι· γρ φύσις δαιμονία, λλ ο
θεία. σημεον δέ· πάνυ γρ ετελες νθρωποι προορατικοί εσι κα εθυόνειροι, ς ο
θεο πέμποντος, λλ σων σπερ ν ε λάλος φύσις στ κα μελαγχολική,
παντοδαπς ψεις ρσιν. (De Divinatione 2.463b12-18)
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
18
In general, since some other animals dream, dreams could not be sent by God and
do not occur for this purpose; however, they are daemonic (δαιμόνια). For nature is
daemonic (δαιμονία), but not divine (ο θεία). A sign of this is that ordinary people
have foresight/prevision (προορατικοί) and vivid dreams (εθυόνειροι), showing that
it is not God who sends them, but such men as have a garrulous (λάλος) and
melancholic (μελαγχολική) nature, see all sorts of sights.
So, God cannot be the sender of dreams, because:
(a) Animals, who do not have intellect/mind (νος), have dreams too.
(b) Quite ordinary people “with low moral and intellectual capacities”,
79
and
especially those whose nature is garrulous and melancholic have vivid dreams
about the future.
Hence, if dreams were sent by God, would be experienced only by those with
“moral and intellectual virtues to the highest degree, and thus approach the divine
level”.
80
The Stageirite also remarks that although dreams are not divine, they are
nevertheless daemonic (δαιμόνια). Dreams are like nature herself “daemonic, but not
divine”. The word “daemonic” does not mean that dreams are “sent by daemons” (cf.
Pythagoras of Samos),
81
but rather “beyond human control”.
82
Dreams must be regarded either as causes τια), signs (σημεα) or coincidences
(συμπτώματα):
νάγκη δ ον τ νύπνια ατια εναι σημεα τν γιγνομένων συμπτώματα,
πάντα νια τούτων ν μόνον. λέγω δ ατιον μν οον τν σελήνην το κλείπειν
τν λιον κα τν κόπον το πυρετο, σημεον δ τς κλείψεως τ τν στέρα εσελθεν,
τ δ τραχύτητα τς γλώττης το πυρέττειν, σύμπτωμα δ τ βαδίζοντος κλείπειν τν
λιον· οτε γρ σημεον το κλείπειν τοτ στν οτατιον, οθ κλειψις το
βαδίζειν. δι τν συμπτωμάτων οδν οτ ε γίνεται οθ ς π τ πολύ. (De
Divinatione 1.426b26-463a3)
Now dreams must be either causes (ατια) or signs (σημεα) of events which occur
or else coincidences (συμπτώματα); either all or some of these, or one only. I use the
word “cause” in the sense in which the moon is the cause of an eclipse of the sun, or
79
Cf. van der Eijk 2005, 190.
80
Op. cit., 190.
81
Diogenes Laertius, Vitae Philosophorum VIII, 32: εἶναι τε πάντα τὸν ἀέρα ψυχῶν ἔμπλεων· κα ταύτας
δαίμονάς τε κα ἤρωας ὀνομάζεσθαι· κα ὑπὸ τούτων πέμπεσθαι ἀνθρώποις τούς τ ὀνείρους κα τὰ σημεῖα
νόσους τε, κα οὐ μόνον ἀνθρώποις λλ κα προβάτοις κα τοῖς λλοις κτήνεσιν. Pythagoras of Samos (582-
496 B.C.), the founder of Pythagoreanism, believed in the divinity of dreams. Daemones (δαίμονες) and
heroes (ἥρωες) are responsible for dreams (ὄνειροι) and signs (σημεῖα). Dreams occur when the soul is
liberated from the sleeping body.
82
van der Eijk 2005, 191.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
19
fatigue is the cause of fever; the fact that a star comes into view I call a “sign” of the
eclipse, and the roughness of the tongue a “sign” of fever; but the fact that someone is
walking when the sun is eclipsed is a coincidence. For this is neither a sign nor a cause
of the eclipse, any more than the eclipse is a cause of sign of a man’s walking. So no
coincidence occurs invariably or even commonly. (trans. W. S. Hett)
Thus, some dreams, as Aristotle notes, may be signs (σημεα) of events happening
in the body of the dreamer. Physicians say that we should pay close attention to
dreams (σφόδρα προσέχειν τος νυπνίοις), because they can help in medical
diagnosis.
83
Also, dreams may become the cause τιον) of our waking actions. The action
(κίνησις) in dream encourages action during the daytime. So, some of the dreams may
be both signs and causes.
84
But, most dreams [prophetic/divinatory dreams], according to the philosopher, are
coincidences (συμπτώματα), “especially all those which are transcendental, and those
in which the origination does not lie in the dreamers themselves, such as in the case of
a naval battle and things taking place far away”.
85
He suggests that, when someone
sees a dream “which is extraordinary either in time, place or magnitude” (λλ
περορίας τος χρόνοις τος τόποις τος μεγέθοις)
86
this is due to an effect like a
ripple in the water or air, where the original movement/impulse (κίνησις) and
sensation (ασθησις) after traveling over a great distance reach the soul of the dreamer.
These movements, says Aristotle, that proceed “from the objects from which
Democritus says, images δωλα) and emanations (πόρροιαι) are thrown off”,
87
reach
the soul more easily at night than by the day, because there is less air at night and
because people perceive small movements more clearly in sleep than in the waking
state.
88
83
De Divinatione 1.463a3-6: ἆρ᾽οὖν στ τῶν ἐνυπνίων τὰ μὲν αἴτια, τὰ δὲ σημεῖα, οἷον τῶν περὶ τὸ σῶμα
συμβαινόντων; λέγουσι γοῦν καὶ τῶν ἰατρῶν οἱ χαρίεντες ὅτι δεῖ σφόδρα προσέχειν τοῖς ἐνυπνίοις.
84
Op. cit. 1.463a21-31: λλ μὴν καὶ ἔνιά γε τῶν καθ᾽ὕπνον φαντασμάτων αἴτια εἶναι τῶν οἰκείων
ἑκάστῳ πράξεων οὐκ ἄλογον· ὥσπερ γὰρ μέλλοντες πράττειν καὶ ἐν ταῖς πράξεσιν ὄντες ἢ πεπραχότες
πολλάκις εὐθυονειρίᾳ τούτοις σύνεσμεν καὶ πράττομεν (αἴτιον δ᾽ ὅτι προωδοποιημένη τυγχάνει κίνησις
ἀπὸ τῶν μεθ᾽ ἡμέραν ἀρχῶν), οὕτω πάλιν ἀναγκαῖον καὶ τὰς καθ᾽ ὕπνον κινήσεις πολλάκις ἀρχὴν εἶναι τῶν
μεθ᾽ ἡμέραν πράξεων διὰ τὸ προωδοποιῆσθαι πάλιν καὶ τούτων τὴν διάνοιαν ἐν τοῖς φαντάσμασι τοῖς
νυκτερινοῖς. οὕτω μὲν οὖν ἐνδέχεται τῶν ἐνυπνίων ἔνια καὶ σημεῖα καὶ αἴτια εἶναι.
85
Op. cit. 1.463b1-3: Τ δὲ πολλὰ συμπτώμασιν ἔοικε, μάλιστα δὲ τά τε ὑπερβατὰ πάντα καὶ ὧν μὴ ν
αὐτος ρχ οἷον περὶ ναυμαχίας καὶ τῶν πόρρω συμβαινόντων.
86
Op. cit. 2.464a2-3.
87
Op. cit. 2.464a11-12: ἀφ᾽ ν κεῖνος τὰ εἴδωλα ποιεῖ κα τὰς ἀπορροίας.
88
Op. cit. 2.463b31-464a19: Περὶ δὲ τῶν μὴ τοιαύτας ἐχόντων ρχς ἐνυπνίων οἵας εἴπομεν,
λλ᾽ὑπερορίας τοῖς χρόνοις τοῖς τόποις τοῖς μεγέθεσιν, τούτων μὲν μηδέν, μὴ μέντοι γε ἐν αὑτος
ἐχόντων τὰς ρχὰς τῶν ἰδόντων τὸ ἐνύπνιον, εἰ μὴ γίνεται τὸ προορᾶν ἀπὸ συμπτώματος, τοιόνδ᾽ ἂν εἴη
μᾶλλον ἢ ὥσπερ λέγει Δημόκριτος εἴδωλα καὶ ἀπορροίας αἰτιώμενος. ὥσπερα γὰρ ὅταν κινήσῃ τι τὸ ὕδωρ ἢ
τὸν ἀέρα, τοῦθ᾽ἕτερον ἐκίνησε, καὶ παυσαμένου ἐκείνου συμβαίνει τὴν τοιαύτην κίνησιν προϊέναι μέχρι τινός,
το κινήσαντος οὐ παρόντος, οὕτως οὐδὲν κωλύει κίνησίν τινα καὶ αἴσθησιν ἀφικνεῖσθαι πρὸς τὰς ψυχὰς τὰ
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
20
II. Aristotelian and Contemporary Views on Sleep and Dreams
In the second part of this paper we shall try to present that when we take an in-
depth study of the function of dreaming, as it is described in the psychological and
biological Aristotelian treatises, we can find great analogies or similarities between the
Aristotelian and the contemporary views on sleep and dreams. R. Mansfield, S.
Goddard and H. Moldofsky assert that “these similarities of content may indicate that
even two millennia of scientific and technological advance have not changed the basic
human observations from which theory and research spring”.
89
Let us start with Aristotle’s empirical observations
90
on the phenomenon of
sleep in animals at 454b15-27 of De Somno et Vigilia (Περ πνου κα
γρηγόρσεως). The ancient philosopher argues that almost all animals, whether
they are aquatic, winged or terrestrial, have the power of sleep. Every kind of
fish, mollusks, insects, hard-eyed animals and every other creature that has eyes
have been seen sleeping. However, all such animals sleep for a short period of
time, and consequently someone may not observe whether they sleep or not. At
the same time, Aristotle notices that it is not easy to determine whether
testaceans, such as mussels and oysters, sleep or not. It is difficult to recognize
sleep in such living beings. But he believes that creatures that are endowed with
sensation (ασθησις), must be capable of sleeping and waking.
Τ μν ον λλα σχεδν πάντα δλα κοινωνονθ΄ πνου͵ κα πλωτ κα πτην κα
πεζ (κα γρ τ τν χθων γνη πντα κα τ τν μαλακων πται καθεδοντα͵ κα
τλλα πνθ σαπερ χει φθαλμος· κα γρ τ σκληρφθαλμα φανερ κα τ ντομα
κοιμμενα· βραχυπνα δ τ τοιατα πντα͵ δι κα λθοι ν τινα πολλκις πτερον
μετχουσι το καθεδειν ο), τν δ΄ στρακοδρμων κατ μν τν ασθησιν οδ πω
γγονε φανερν ε καθεδουσιν· ε δ τ πιθανς λεχθες λγος͵ τοτ πεισθσεται.
τι μν ον πνου κοινωνε τ ζα πντα͵ φανερν κ τοτων· τ γρ ασθησιν
χειν ρισται τ ζον͵ τς δ΄ ασθσεως τρπον τιν τν μν κινησαν κα οον δεσμν
τν πνον ενα φαμεν͵ τν δ λσιν κα τν νεσιν γργορσιν. (De Somno 1.454b15-
27)
ἐνυπνιάζουσας, ἀφ᾽ ν κεῖνος τὰ εἴδωλα ποιεῖ κα τὰς ἀπορροίας, καὶ ὅπῃ δὴ ἔτυχεν ἀφικνουμένας μᾶλλον
αἰσθητὰς εἶναι νύκτωρ διὰ τὸ μεθ᾽ ἡμέραν φερομένας διαλύεσθαι μᾶλλον (ἀταραχωδέστερος γὰρ ἀὴρ τῆς
νυκτὸς διὰ τὸ νηνεμωτέρας εἶναι τὰς νύκτας), καὶ ἐν τῷ σώματι ποιεῖν αἴσθησιν διὰ τὸν ὕπνον, διὰ τὸ κα τῶν
μικρῶν κινήσεων τῶν ντὸς αἰσθάνεσθαι καθεύδοντας μᾶλλον ἐγρηγορότας. αὗται δ᾽ αἱ κινήσεις
φαντάσματα ποιοῦσιν, ἐξ ὧν προορῶσι τὰ μέλλοντα περὶ τῶν τοιούτων.
89
Mansfield, Goddard, Moldofsky 2003, 60.
90
Preus 1957, 21: “Aristotle’s sources of biological information were of three general sorts: 1) written
sources, literary, philosophical, and otherwise; 2) the oral tradition and interviews with fishermen,
farmers and others; 3) his own dissections and observations”. Although he relied upon written sources
and oral tradition, he observed many phenomena ἰδίοις ὄμμασι (with his own eyes).
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
21
Practically all other animals, aquatic, winged and terrestrial, partake in sleep (for all
kinds of fish and mollusks have been observed asleep, and all other animals which
have eyes; for clearly even hard-eyed animals and insects repose, but these creatures
only sleep for a short time, so that one might often doubt whether they partake in sleep
or not), but in the case of the testacea direct observation has not yet proved whether
they sleep or not. But if the foregoing argument appeals to anyone, he will be satisfied
that they do.
Therefore that all animals partake in sleep is obvious from the following
considerations. The animal is defined by the possession of sensation, and we hold that
sleep is in some way the immobilization or fettering of sensation, and that the release
or relaxation of this is waking. (trans. W. S. Hett)
Furthermore, Aristotle at Historia Animalium (Περ τ Ζα στορίαι), iv 10.536b25-
537b22 offers a more detailed description of the phenomenon of sleep in animals that
are blooded (ναιμα) and have legs (πεζά), fish (χθύες), mollusks (μαλάκια),
crustaceans (μαλακόστρακα), insects (ντομα), hard-eyed animals (σκληρόφθαλμα)
and every other creature that has eyes. Also, he notices that:
τι δ νυπνιάζειν φαίνονται ο μόνον νθρωποι, λλ κα πποι κα κύνε κα βόες,
τι δ πρόβατα κα αγες κα πν τ τν ζοτόκων κα τετραπόδων γένος· δηλοσι δ
ο κύνες τ λαγμ. περ δ τν οτοκούντων τοτο μν δηλον, τι δ καθεύδουσι,
φανερόν. μοίως δ κα τ νυδρα, οον ο τ χθύες κα τ μαλάκια κα τ
μαλακόστρακα, κάραβοί τε κα τ τοιατα. Βραχύυπνα μν ον στι πάντα τατα,
φαίνεται δ καθεύδοντα. (Historia Animalium iv 10.536b27-537a2)
It appears, that it is not only human beings who dream (νυπνιάζειν), but also
horses, and dogs, and cattle, and further sheep, and goats, and all viviparous
quadrupeds; and dogs show it by barking in their sleep. As far as it concerns oviparous
animals, it is not sure that they dream, but it is obvious they sleep. And the same holds
for water animals, such as fish and molluscs, and crustaceans, crayfish and the like.
All these animals sleep, undoubtedly, but their sleep is for a short period of time.
Decades of research have shown and therefore have confirmed the Aristotelian
view that “practically all other animals…partake in sleep”. We now know with
reasonable certainty that all mammals and birds sleep.
Many studies have shown that all mammals and birds experience REM (‘Rapid Eye
Movement Sleep’)
91
and non-REM sleep, but with some differences. REM and non-
REM sleep episodes are quite shorter in birds than in mammals. “Their NREM sleep
91
Two sleep researchers at the University of Chicago, Nathaniel Kleitman and his student Eugene
Aserinsky, discovered the rapid-eye movement (REM) sleep and its association with dreaming in 1953.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
22
episodes average only 2 ½ minutes, and REM sleep episodes only 9 seconds”,
92
whereas in humans, for example, the average length of non-REM and REM sleep is
about 90 to 120 minutes.
The following table lists the average sleep time for various mammals in over a 24-
hour period:
93
Mammals
Average Daily Sleep Time (in
hours)
Giraffe
1.9
Elephant
3.6
Whale
5.3
Human
8.0
Baboon
9.4
Domestic Cat
12.5
Laboratory rat
13.0
Lion
13.5
Squirrel
15.9
Big Brown Bat
20
Koala
The longest sleeping animal 22
Researchers have now been able to show that fish, hard-shelled animals, mollusks
and insects ‘sleep’, but not in the same way as mammals and birds do. Since most fish
do not have eyelids
94
(except from sharks),
95
they ‘sleep’ or ‘rest’ with their eyes open
during the day or at night. They go into a state of inactivity. Hard-shelled animals,
mollusks and insects experience some kind of repose, too.
96
92
See Sleep Research Society 1997, <http://www.sleepsources.org/uploads/sleepsylla
bus/m.html>.
93
This table was adapted from the following sources: (a) Kryger, Avidan and Berry (eds) 2014, 68-
69, (b) Allada and Siegel 2008, R671, (c) Sleep Research Society 1997,
<http://www.sleepsources.org/uploads/sleepsyllabus/m.html>.
94
Eyelid’s function is to keep the eye moist, because the eye’s outermost layer, the cornea, must be
kept moist. Most fish do not have lachrymal glands and eyelids, because they live in water that keeps
their eyes moist.
95
Sharks have a nictitating membrane, which can be pulled down over the eye.
96
Cf. McNamara, Barton and Nunn (eds) 2010.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
23
Aristotle, as we have already said, asserts that sleep provides rest (νάπαυσις)
to the sense organs, since all bodily parts, which have a natural function, are
unable to act continuously without interruption.
τι σων στί τι ργον κατ φύσιν, ταν περβάλλ τν χρόνον δύναται χρόν τι
ποιεν, νάγκη δυνατεν, οον τ μματα ρντα κα παύεσθαι τοτο ποιοντα,
μοίως δ κα χερα κα λλο πν ο στί τι ργον. ε δ τινός στιν ργον τ
ασθάνεσθαι, κα τοτο ν περβάλλ σον ν χρόνον δυνάμενον ασθάνεσθαι
συνεχς, δυνατήσει κα οκέτι τοτο ποιήσει. (De Somno 1.454a26-32)
for all things that have a natural function, as soon as they exceed the time for which
they are able to do a certain thing, must become impotent, e.g. the eyes by exercising
vision [must become impotent], and must cease from doing it, and similarly the hand,
and everything else that has a function. So if sense perception is the function of some
part, this too, if it exceeds the due time for which it is capable of perceiving
continuously, will become powerless, and will do so no longer.
πρτον μν ον πειδ λέγομεν τν φύσιν νεκά του ποιεν, τοτο δ γαθόν τι, τν
δ νάπαυσιν παντ τ πεφυκότι κινεσθαι, μ δυναμέν δ ε κα συνεχς κινεσθαι
μεθ δονς ναγκαον εναι κα φέλιμον, τ δ πν αυτ τ ληθεί προσάπτουσι
τν μεταφορν ταύτην ς ναπαύσει ντι· (De Somno 2.455b17-21)
First of all then, since we assert that nature acts for the sake of an end, and that this
end is a good, and that to everything that moves by nature, but cannot move constantly
and continuously with pleasure, rest is necessary and beneficial; and the metaphorical
term of sleep as ‘rest’ “reflects the literal truth”
97
.
Consequently, sleep for Aristotle is a good thing and serves a restorative function.
It helps the body to rest and rejuvenate. This view has been frequently explored in
modern and contemporary era.
98
Modern sleep research started in the 1930s with the
invention of the electroencephalography (EEG). The advent of new technology has
allowed scientists to study sleep in a systematic and objective way, and to develop a
number of different theories in order to explain the function/purpose of sleep.
“Among the major theories that have been formulated to explain the
function/purpose of sleep is the repair/restorative theory (e.g., Webb 1981; cf: Cohen
1979; Shapiro 1982), which suggests that sleep serves an important recuperative
function, allowing one to recover not only from physical fatigue, but also from
emotional and intellectual demands”.
99
Two of the most important repair/restorative theories are those of Oswald (1969, 1980)
and Horne (1988). The British sleep researcher, I. Oswald, asserted that non-REM sleep
97
Gallop 1996, note 6, 70 and 71.
98
Cf. Mansfield, Goddard, Moldofsky 2003, 61.
99
Roeckelein 1998, 437.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
24
restores bodily functions that have deteriorated at the end of the day, while REM sleep
replenishes mental functions, through the stimulation of protein synthesis that is
increased during sleep and is needed for the restoration of bodily tissue and cell
growth. Oswald pointed out that there is a substantial release of growth hormone from
the pituitary gland during deep non-REM sleep. This hormone stimulates protein
synthesis.
J. Horne’s (1988) restorative theory resembles that of Oswald’s (1980). Horne
believed that sleep is divided into core sleep (REM and non-REM) and optional sleep
(lighter stages of non-REM). Core sleep is essential for the restoration and the
maintenance of the brain, while “optional sleep, as its name implies, is not essential
for normal functioning of either the brain or the body”.
100
The basic difference between the two theories is that Oswald suggested that non-
REM sleep restores bodily processes that have been active during the day, whereas
Horne does not.
Aristotle says that sleep takes place especially after the ingestion of food (κ τς
περ τν τροφν ναθυμιάσεως),
101
while awakening occurs, when the process
of digestion is finished (ταν πεφθ κα κρατήσ συνεωσμένη θερμότης).
102
Therefore, the philosopher connects food ingestion and digestion with the
sleep-wake cycle. For Mansfield, Goddard and Moldofsky “this notion is
evident in recent studies which describe how different feeding programs can
alter the sleep-wake cycle of rats via input from the vagus nerve
103
or
entrainment of the circadian clock in the liver
104
”.
105
Hansen et al. (1998) examined the effects of a “cafeteria diet” on sleep-wake activity
and brain temperature (Tbr) in control and vagotomized rats for 7 consecutive days.
The researchers found that in control rats, the “cafeteria diet” consisting of palatable
high fat foods, “resulted in an increase in non-REM sleep, which was due to a
significant lengthening of the non-REM sleep episodes, and in a decrease in REM
sleep”.
106
In contrast, “in vagotomized rats, cafeteria feeding resulted in a decrease in
both non-REM sleep and REM sleep”.
107
Furthermore, cafeteria diet increased brain
temperature (Tbr) in both control and vagotomized rats.
100
Green 2011, 66.
101
De Somno 3.456b18-19.
102
Op. cit. 3.458a10-11.
103
Hansen et al. 1998, R172: “The vagus nerve is an important communication pathway between the
gastrointestinal tract and the central nervous system”.
104
Cf. Stokkan et al. 2001, 490-493, demonstrated that there is a link between feeding and the liver
clock, that functions independently of the master clock in the Suprachiasmatic Nucleus (SCN) and the
light cycle.
105
Mansfield, Goddard, Moldofsky 2003, 61.
106
Hansen et al. 1998, R172.
107
Op. cit., R172.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
25
Roky et al. (1999) in their study showed that food and water restriction to the light
period for 29 days changed the sleep-wake cycle of Sprague-Dawley rats. During this
period, the daily rhythm of REM sleep and temperature of the brain (Tbr) were
reversed, while the distribution of non-REM sleep between the sleep and wake cycles
was attenuated.
108
Aristotle describes sleep as the cooling of the ‘primary sense-faculty’ or
‘primary sensitive/perceptive part’ (πρτον ασθητικόν), which is located in
the heart. The region around the brain acts as a coolant during sleep, while the
things that cause sleeping are hot. Accordingly, during sleep the body
temperature goes up and down.
τς μν ον κινήσεως φανερν τι κα το πνεύματος ρχ κα λως τς
καταψύξεώς στιν νταθα [τ περ τν καρδίαν μέρος]. (De Somno 2.456a6-8)
Now, as for movement, it is obvious that the origin of breathing and the cooling
process in general, is found there [the region about the heart].
τν μν πνον εναι κατάψυξιν, τ δ ατια το καθεύδειν θερμά. (De Somno 3.457b9-
10)
sleep should be a cooling process, while the causes of sleep are hot.
ο μν λλ κύριός γ στν τόπος περ τν γκέφαλον, σπερ ν λλοις ερηται.
πάντων δ στ τν ν τ σώματι ψυχρότατον γκέφαλος, τος δ μ χουσι τ
νάλογον τούτ μόριον. (De Somno 3.457b27-31)
the region about the brain, however, is the dominant factor, as has been said
elsewhere. The brain, or the analogous part in animals that have no brain, is the coldest
of all parts of the body.
Several types of evidence in recent times support the view that sleep onset is
associated with body cooling in several species. “Sleep onset in humans is associated
with a reduction of body temperature of 1o to 2o C accompanied by heat loss due to
vasodilation [widening of blood vessels] and increased sweating”.
109
Body
temperature is controlled by the preoptic area/anterior hypothalamus (also called
PO/AH), where there are neurons sensitive in skin and blood temperatures
(temperature-sensitive neurons).
During periods of non-REM (NREM) sleep or slow-wave sleep (SWS), the
temperature of both the brain and body decrease. The longer the non-REM sleep
episode, the more the temperature falls. In contrast, the temperature of the brain
increases during REM sleep.
108
Roky et al. 1999, 697.
109
Chokroverty 1994, 68.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
26
“Many mammals lose significant thermal regulatory capacity during sleep. Some
animals like squirrels go into a torpor state during sleep, in which their body
temperature dips well below the normal level for hours at a time”.
110
McGinty and
Szymusiak hypothesize that:
111
slow-wave sleep (SWS) in mammals and birds is controlled by thermoregulatory
mechanisms, and provides brain and body cooling as a primary homeostatic feedback
process…Studies have shown that SWS, like other heat loss processes, is facilitated
when brain temperature exceeds a threshold level. This threshold is hypothesized to
be determined by responses of PO-AH thermosensitive neurons and to be regulated
by both circadian and homeostatic processes…At a functional level, SWS-induced
brain and body cooling would provide several adaptations including lower energy
utilization, reduced cerebral metabolism, protection of the brain against the sustained
high temperatures of wakefulness, facilitation of immune defense processes and
regulation of the timing to behavioral activity relative to the circadian light-dark
cycle.
112
According to Mansfield, Goddard and Moldofsky, “Aristotle’s theory of the
final cause of sleep being animal preservation [νεκα σωτηρίας] is also revisited
in contemporary thinking”.
113
στε σωτηρίας νεκα τν ζων πάρχει. (De Somno 2.455b22)
it follows that sleep exists for the preservation/conservation of animals.
ξ νάγκης μν γινόμενος (ο γρ νδέχεται ζον εναι μ συμβαινόντων τν
περγαζομένων ατό), νεκα δ σωτηρίας· σζει γρ νάπαυσις. (De Somno 3.458a29-
32)
sleep occurs of necessity (for it is not possible for an animal to exist, if the conditions
that produce it not obtain), and sleep exists for its preservation/conservation; for rest
preserves/conserves.
One of the major and earliest theories that have been formulated to explain the
function/purpose of sleep is the adaptive non-responding theory (Webb 1974),
114
also
known as evolutionary/circadian theory (Kleitman 1963). This theory suggests that sleep
has evolved as a means of conserving energy and promoting survival by keeping
organisms out of harm’s way at times when they would be most vulnerable. Sleep
110
See Sleepdex 2013, <http://www.sleepdex.org/thermoregulation.htm>.
111
See Mansfield, Goddard, Moldofsky 2003, 60-61.
112
McGinty, Szymusiak 1990, 480.
113
Mansfield, Goddard, Moldofsky 2003, 61.
114
Webb 1974, 1023: “We have chosen to use the term non-responding to mean qualitatively minimal
behavioral engagement with the surround”.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
27
protects animals from predators, and permits them to better adapt to their
environment (Meddis 1975).
The adaptive non-responding theory is supported by comparative research of different
animal species. Animals that have less predation risks (e.g., lions), sleep longer than
prey species (e.g., giraffes). Sleep time is reduced in prey species, as they have to
remain alert and aware of nearby predators.
It is interesting to note that Aristotle associates epilepsy (πιληψία)
115
with
sleep. He regards sleep as a kind of an epileptic fit, but not a pathological one.
He remarks:
τ γρ παιδία καθεύδει σφόδρα δι τ τν τροφν νω φέρεσθαι πσαν. σημεον δ
τ περβάλλειν τ μέγεθος τν νω πρς τ κάτω κατ τν πρώτην λικίαν, δι τ π
τατα γίνεσθαι τν αξησιν. δι ταύτην δ τν ατίαν κα πιληπτικ γίνεται· μοιον
γρ πνος πιλήψει, κα στι τρόπον τιν πνος πίληψις. δι κα συμβαίνει πολλος
ρχ τούτου το πάθους καθεύδουσιν, κα καθεύδοντες μν λίσκονται, γρηγορότες
δ ο· ταν γρ πολ φέρηται τ πνεμα νω, καταβανον πάλιν τς φλέβας γκο, κα
συνθλίβει τν πόρον δι ο ναπνο γίνεται. (De Somno 3.457a12-14)
for children sleep very much, because all their food rises upwards. A proof of this
whereof seems in the excessive size of the upper parts compared with the lower during
early childhood, because growth takes place in these parts. Hence too they are liable
to epilepsy, for sleep is like epilepsy; in fact, sleep is, in a way, epilepsy. That is why
for some people the beginning of this affection happens during sleep, and they become
seized with it while asleep, but not while awake. For when a great mass of pneuma
moves upwards, it swells the blood-vessels as it descends again, and
compresses/constricts the passage through which respiration passes.
The philosopher thinks of sleep, like epilepsy, as a temporary failure of
consciousness. He observes the occurrence of epileptic seizures during sleep
116
and
says that children are “particularly prone to the disease (a widely known fact in
antiquity)”.
117
These observations somehow prefigure the contemporary type of
115
For the history of epilepsy see Temkin 1971. Epilepsy was generally believed to be of divine origin.
It was regarded as a ‘sacred disease’. The earliest mention of epileptic seizures can be traced back to
2,000 B.C. in ancient Mesopotamia. In 400 B.C. Hippocrates of Kos (460-370 B.C.), the father of medicine,
in his treatise De Morbo Sacro (Περὶ ερῆς Νοῦσου), disputes the divine origin of epilepsy and describes
it as a natural disease. Cf. Hippocrates, De Morbo Sacro 1.1-6: Περὶ τῆς ερῆς νούσου καλεομένης ὧδ᾽ ἔχει.
οὐδέν τί μοι δοκεῖ τῶν ἄλλων θειοτέρη εἶναι νούσων οὐδὲ ἱερωτέρη, λλ φύσιν μὲν ἔχει καὶ πρόφασιν, οἱ δ᾽
ἄνθρωποι ἐνόμισαν θεῖόν τι πρῆγμα εἶναι ὑπὸ ἀπειρίης καὶ θαυμασιότητος, ὅτι οὐδὲν ἔοικεν ἑτέροισι. The
two Hippocratic treatises De Morbo Sacro (Περὶ ερῆς Νοῦσου) and Chapter 14 of De Flatibus ((Περὶ Φυσῶν)
provide an in-depth etiological account of epilepsy. Also, many other medical treatises of the
Hippocratic Corpus contain references to epilepsy. Hippocrates was the first physician to attribute the
etiology of epilepsy to brain disorder.
116
Both Hippocrates and Aristotle observed the relationship between sleep and epileptic seizures.
117
Cf. van der Eijk 2005, 134.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
28
‘absence seizures’ (formerly called ‘petit mal’ seizures),
118
that usually occur in school-
aged children and young people.
119
According to Lo Presti “Aristotle’s association of epilepsy with sleep is anything but
a unique example in the history of the medical representation of epilepsy”.
120
However, the relationship of epilepsy and sleep was not studied until the second half
of the nineteenth century. In 1885, the British neurologist William Richard Gowers
examined the effect of the sleep/wake cycle on ‘grand mal’ seizures.
121
In 1890, the
French neurologist Charles Féré described specific sleep disorders associated with
epilepsy. But in the electroencephalography (EEG) period
122
Professor Pierre
Passouant and colleagues,
123
were the first to report an association between
epileptiform discharges (EDs) and sleep phasic phenomena.
Aristotle in lines 462a6-8 of De Ιnsomniis mentions that “(for often, while
someone is asleep, there is something in the soul which says that this
phenomenon [what is appearing] is a dream); but if he is not aware that he is
asleep, then there is nothing which will contradict the imagination” [(πολλάκις
γρ καθεύδοντος λέγει τι ν τ ψυχ τι νύπνιον τ φαινόμενον)· ἐὰν δ
λανθάν τι καθεύδει, οδν ντιφήσι τ φαντασί]. This view is one of the first
written historical descriptions of lucid dreaming in the Western civilization. Lucid
dreaming is the conscious dreaming, is a phenomenon, according to which a
person who is asleep and dreaming he becomes consciously aware in his dream
that he is dreaming.
Frederik Willem van Eeden (1860-1932), a Dutch psychiatrist, used for the first time
the term ‘lucid dreaming’:
124
The seventh type of dreams, which I call lucid dreams, seems to me the most
interesting and worthy of the most careful observation and study. Of this type I
118
‘Absence seizures’ (they are also called ‘petit mal’ seizures) are seizures that usually last a few
seconds and involve a brief impairment of consciousness. Chokroverty 1994, 433: “Absence seizures
occurring during sleep are difficult to diagnose and clinical absence seizures are observed in the waking
state. According to Niedermeyer there may be fluttering of the eyelids during the spike and wave
discharges in sleep. Gastaut and colleagues and Patry et al described occasional cases of petit mal status
in REM sleep”.
119
Lo Presti 2013, 208.
120
Op. cit., 206.
121
‘Grand mal’ seizures, or generalized tonic-clonic seizures, are seizures that occur almost
exclusively in non-REM sleep and affect the entire body. They involve loss of consciousness and violent
muscle contractions. Chokroverty 1994, 433: “Primary generalized ‘grand mal’ seizure occurs almost
exclusively in non-REM sleep and is most frequently seen 1-2 hours after sleep onset and at 5-6 a.m. as
noted originally in 1985 by Gowers and later by others. Grand mal seizure may occur only during sleep,
only during daytime or randomly distributed”.
122
The electrοencephalography was invented in 1929 by the German physiologist and psychiatrist
Hans Berger (1873-1941).
123
Passouant, Cadilhac, Philippot 1951, 659-663.
124
See van Eeden 1913, 431-461.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
29
experienced and wrote down 352 cases in the period between January 20, 1898, and
December 26, 1912.
In these lucid dreams the reintegration of the psychic functions is so complete that
the sleeper remembers day-life and his own condition, reaches a state of perfect
awareness, and is able to direct his attention, and to attempt different acts of free
volition. Yet the sleep, as I am able confidently to state, is undisturbed, deep and
refreshing.
125
Surprisingly, the father of psychoanalysis, Sigmund Freud (1856-1939), mentioned
lucid dreams very briefly. He added a paragraph in the 1909-second edition of his
classic work The Interpretation of Dreams (Die Traümdeutung 1899), and another one to
the book’s fourth edition in 1914. “Even there, he doesn’t mention lucid dreaming by
name, despite having met and corresponded with Frederic van Eeden…who coined
the term ‘lucid dream’ in his seminal 1913 article, ‘A Study of Dreams’”
126
:
On the other hand, there are some people who are quite clearly aware during the
night that they are asleep and dreaming and who thus seem to possess the faculty of
consciously directing their dream. If, for instance, the dreamer of this kind is
dissatisfied with the turn taken by a dream, he can break it off without waking up and
start it again in another direction just as a popular dramatist may under pressure
give his play a happier ending. Or another time, if his dream has led him into a sexually
exciting situation, he can think to himself:’I won’t fo on with this dream any further
and exhaust myself with an emission; I’ll hold it back for a real situation.
The Marquis d’ Hervey de Saint-Deny… claimed to have acquired the power of
accelerating the course of his dreams just as he pleased, and of giving them any
direction he chose. It seems as though in his case the wish to sleep had given place to
another preconscious wish, namely to observe his dreams and enjoy them. Sleep is just
as compatible with a wish of this sort as it is with a mental reservation to wake up if
some particular condition is fulfilled.
127
Lucid dreams have been proven scientifically to exist. The first scientific research
on lucid dreaming was Celia Green’s 1968 study Lucid Dreams.
128
Furthermore, Keith
Hearne produced the first laboratory evidence of lucid dreaming in the late 1970’s.
129
In the early 1980s the psychophysiologist Stephen LaBerge made the study of lucid
dreaming into a science by demonstrating its existence.
130
He “validated the psycho-
125
van Eeden 1913, <http://www.lucidity.com/vanEeden.html>.
126
Thomson 2015, 143.
127
Freud 2010, 571.
128
Cf. Celia Green 1968.
129
Cf. Hearn 1978.
130
Cf. LaBerge 1985.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
30
physical markers of lucidity with an EEG machine”.
131
In 2009 the psychiatrist Allan
Hobson
132
linked lucid dreaming to consciousness. Researchers continue to conduct
scientific experiments in order to learn more about this fascinating and complex
phenomenon.
The Macedonian philosopher refers briefly to the phenomenon of
somnambulism or noctabulism(sleep-walking). In lines 456a25-26 of De Somno
he says that “some people move in their sleep and do many waking acts but not
without any (mental) image/representation and sensation” (Κινονται δ΄ νιοι
καθεδοντες κα ποιοσι πολλ γρηγορικ, ο μέντοι νευ φαντάσματος κα
ασθήσεώς τινος).
Somnambulism (from the Latin somnus = sleep and ambulare = to walk around) has
been described since before the time of Hippocrates and it has puzzled people for
centuries. It is a mysterious behaviour, a sleep disorder (parasomnia). The advances in
technology and the development of Neuroscience from the second half of the twentieth
century have led to an increasingly understanding of this intriguing phenomenon.
Recent researches have discovered that somnambulism most often occurs during the
non-REM sleep stage early in the nightwithin the first third or first half of the sleep
period. It “involves a series of complex motor behaviors and results in walking during
altered consciousness”.
133
Aristotle in lines 458b16-20 of De Insomniis mentions that when we are asleep,
we sometimes think (ννοομεν) it functions the rational (νοητικόν) or
discursive (διανοητικόν) part or faculty of the soul something else besides
the phantasmata. And he adds that “this would become obvious to anyone if he
concentrates and tries to remember [it functions memory] his dream
immediately upon rising” (trans. W. S. Hett):
τι παρ τ νπνιον ννοομεν λλο τι͵ καθπερ ν τ γρηγορναι ασθανμενο
τι· περ ο γρ ασθανμεθα͵ πολλκις κα διανοομεθ τι. οτω κα ν τος πνοις παρ
τ φαντσματα νοτε λλα ννοομεν, φανεη δ΄ ν τ τοτο͵ ε τις προσχοι τν νον
κα πειρτο μνημονεειν ναστς.
So, according to Aristotle’s remarks on the previous paragraph, we realize that there
is a mental activity in dreams similar to the activity we have in waking life while we
are perceiving something. This view is supported by modern and contemporary
studies on sleep creativity. Dreams can be used for decision-making and creative
problem solving. In 1892, Charles M. Child did the first study on sleep creativity. Child
asked 186 students if they had ever solved a problem during sleep. One third said they
131
Hurd 2009, <http://www.dreaminglucid.com/articles/The%20Science%20of%
20Lucid%20Dreaming.pdf>.
132
Cf. Hobson 2002. Idem. 2009, 41-44.
133
Harris-Thorpy 2012, 189.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
31
had. In 1993, Deirdre Barrett, a clinical psychologist at Harvard Medical School,
conducted an experiment asking 76 college students to choose a real-life homework
problem and incubate answers. She found that at the end of a week, half of the students
had dreamed about the problem, and about a quarter had a dream that contained a
solution.
134
Barrett came to the conclusion that “dreams are thinking or problem
solving
135
in a different biochemical state from that of waking”.
136
The philosopher believed that dreaming is not the work of actual perception,
since external sense objects/stimuli are absent during sleep. But the affection
(πάθος) produced by them (external sense objects/stimuli correspond to each
sensory organ and produce sense-perception in us) persists in the sense organs,
not only when the sense organs are actualized, but even when the external
stimuli have gone:
Τ δ στ τ νύπνιον κα πς γίνεται, κ τν περ τν πνον συμβαινόντων μάλιστ
ν θεωρήσαιμεν. τ γρ ασθητ καθ καστον ασθητήριον μν μποιοσιν ασθησιν,
κα τ γινόμενον π ατν πάθος ο μόνον νυπάρχει ν τος ασθητηρίοις
νεργουσν τν ασθήσεων, λλ κα πελθουσν. (De Insomniis 2.459a24-28)
This means that dreams, according to Aristotle, are manifestations of internal
sensations (κα πελθόντος το θύραθεν ασθητο μμένει τ ασθήματα ασθητ ντα,
op. cit. ii 460b 2-3), which are expressed as ‘dream imagery’.
The above view is analogous to contemporary clinico-anatomical studies on
dreaming or ‘dream imagery’. In the dream state the external sensory perception is
limited/suspended, while ‘dream imagery’ is generated by “projecting information
backward in the [visual] system” (Kosslyn), so that “internally generated images
which are fed backwards into the [visual] cortex as if they were coming from outside”
(Zeki).
137
Aristotle was probably one of the first who made remarks on ‘hypnagogic’
(state of consciousness that marks the onset of sleep/the period of transition
134
Barrett 1993, 115-123. Barrett in her book entitled The Committee of Sleep (2001), describes how
some of the most creative personalities in the fields of science (Einstein), music (Beethoven, Beatles),
politics (Ghandi) etc. used their dreams for creative problem solving.
135
G. William Domhoff is against any problem-solving theory of dream function. He argues that
“creative thinking during sleep does not mean that dreams have a problem-solving function” Cf.
Domhoff 2003, http://www2.ucsc.edu/dreams/Library/domhoff_
2004b. html.
136
Barrett, McNamara 2007, xiv.
137
Cf. Kosslyn 1994, 74; Zeki 1993, 326.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
32
into sleep)
138
and ‘hypnopompic’ (the transition from sleep to wakefulness)
139
phenomena/hallucinations:
τι δ ληθ λγομεν κα εσ κινσεις φανταστικα ν τος ασθητηροις͵ δλον, ἐάν
τις προσχων πειρται μνημονεειν πσχομεν καταφερμενο τε κα γειρμενοι·
νοτε γρ τ φαινμενα εδωλα καθεδοντι φωρσει γειρμενος κινσεις οσας ν
τος ασθητηροις· νίοις γρ τν νεωτέρων κα πάμπαν διαβλέπουσιν, ἐὰν σκότος,
φαίνεται εδωλα πολλ κινούμενα, στ γκαταλύπτεσθαι πολλάκις φοβουμένους. (De
Insomniis 3.462a8-15)
It becomes clear that our statement is true, and that there are movements of
imagination in the sense organs, if one attentively tries to remember how we are
affected when falling asleep or waking up; For sometimes one will detect, when
waking up, that the images which appear in sleep are movements in the sense organs;
Indeed some very young people, even when their eyes are wide open, if it is dark,
many moving images appear, so that they often conceal themselves in terror.
The Stageirite carefully observes that some people experience images (εδωλα)
between sleeping and waking. When waking up, occasionally it is possible to detect
these images as movements of imagination (κινσεις φανταστικαί) in the sense organs.
David Gallop correctly says that Aristotle “does not explain how [these images] are
detected. But he takes them as evidence for movements subsisting within the eyes, like
the frightening objects seen in the dark by children, which they vainly try to shut out
by covering their heads”.
140
The investigation of these perceptual phenomena began in the 19th century through
the research works of Johannes Peter Müller (1826), Jules Gabriel François Baillanger
(1846), Louis-Ferdinand-Alfred Maury (1848),
141
and it continues until today.
Hypnagogic or hypnopompic hallucinations are usually visual, auditory, tactile,
olfactory or more complex sensory phenomena taking place between sleeping and
waking. “Taken together, hypnagogic and hypnopompic hallucinations are referred to
as ‘hypnagogia [cf. Mavromatis 1987]”.
142
During hypnagogia the affected person may
see visions (e.g. coloured circles, faces), hear sounds (e.g. bangs, vocal or instrumental
music), smell unpleasant odors etc. that aren’t there. These phenomena are quite vivid,
last from a few seconds to more than fifteen minutes, and are usually associated with
narcolepsy (a chronic neurological disorder).
138
The term ‘hypnagogic’ [from the Ancient Greek words ‘ὕπνος’ (sleep) and ‘ἀγωγός’ (leader)] was
introduced by the French psychologist Louis-Ferdinand-Alfred Maury (1817-1892).
139
The term ‘hypnopompic’ [from the Ancient Greek words ὕπνος’ (sleep) and ἀγωγός’ (leader)]
was coined by the British physical researcher Frederic W. H. Myers (1834-1901).
140
Gallop 1996, 152-153.
141
Blom 2010, 251.
142
Blom 2010, 251.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
33
Aristotle tells us that external or somatic stimuli become a part of a dream. For
example faint noises in our ears sound like a thunder or a lightening; a very
slight heat in any part of the body is felt like walking through fire:
δλον δ π τν συμβαινόντων κατ τος πνους πολλάκις· οονται γρ
κεραυνοσθαι κα βροντσθαι μικρν χων ν τος σ γινομένων, κα μέλιτος κα
γλυκέων χυμν πολαύειν καριαίου φλέγματος καταρρέοντος, κα βαδίζειν δι
πυρς κα θερμαίνεσθαι σφόδρα μικρς θερμασίας περί τινα μέρη γιγνομένης.
πεγειρομένοις δ τατα φανερ τοτον χοντα τν τρόπον. (De Divinatione 1.463a11-
17)
This is clear from what often happens in sleep; dreamers think it is lightning and
thundering, when faint noises fall upon their ears, and they are enjoying honey and
sweet flavours, when a tiny drop of phlegm is flowing down [the oesophagus], and
they are walking through fire and feeling extremely hot, when a very slight heat is
affecting certain parts of the body. But when they wake up, it becomes obvious that
these things have a true character.
It has been showed by numerous scientific researches that external sensory stimuli
(e.g. sounds, smells and physical sensations) are sometimes incorporated into the
dream scene, while the dreamer is still asleep. This phenomenon is called ‘dream
incorporation’. “A range of stimuli of varying modalities, such as water droplets on
the skin (Dement & Wolpert, 1958), positive and negative odours (Schredl, Atanasova,
Hörmann, Maurer, Hummel & Stuck, 2009), and sounds (Berger, 1963) have all been
incorporated into dream content, either directly or in disguised form”.
143
A famous painting by Salvador Dali, titled ‘Dream Caused by The Flight of a Bee
around a Pomegranate a Second Before Awakening’ (1944), depicts this phenomenon.
In this oil painting Dali depicts his wife, Gala, in the midst of a dream. Two droplets
of water and a small pomegranate float below Gala’s naked body. Above the
pomegranate flies a bee. Gala’s dream, caused by the noise of the bee, appears in the
upper part of the painting. From a large pomegranate bursts out a fish, from whose
mouth two tigers spews out together with a bayonet (a symbol of the stinging bee)
which, one second later, will sting Gala in the arm and wake her up.
144
Aristotle’s natural theory of how prophetic/divinatory dreams “which are
extraordinary either in time, place or magnitude” and consequently are not
mere coincident, might come about, “is in fact, better suited to telepathy than
143
Bloxham, Durrant 2014, 129.
144
Alarcó, http://www.museothyssen.org/en/thyssen/ficha_obra/352 : “Dali explained in 1962
that in this dream, which takes place in broad daylight, he had the idea of ‘putting into an image for the
first time Freud’s discovery of the typical dream involving a long story argument, resulting from the
instantaneity of an accident causing awakening. Just as the dropping of a rod on the neck of a sleeper
gives rise simultaneously to his awakening and to a very long dream ending with the descent of the
guillotine blade, here the sound of the bee provokes the sensation of the sting which wakes Gala’”.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
34
to precognition [foresight], as is the hypothesis of special rapport between
distant friends”:
145
τ δ τινας εθυονείρους εναι κα τ τος γνωρίμους περ τν γνωρίμων μάλιστα
προορν συμβαίνει δι τ μάλιστα τος γνωρίμους πρ λλήλων φροντίζειν· σπερ
γρ πόρρω ντων μάλιστα γνωρίζουσι κα ασθάνονται, οτω κα τν κινήσεων· α γρ
τν γνωρίμων γνωριμώτεραι κινήσεις. (De Divinatione 1.464a27-32)
That some persons have vivid dreams, and that familiar friends have
foresight/prevision especially about each other is due to the fact that familiar friends
care most for each other; for as [familiar friends] in particular recognize and perceive
each other at a distance, so too in the case of movements; for the movements/impulses
of familiar friends are themselves more familiar.
The above excerpt explains why friends have dreams about each other: their sensory
movements/impulses (κινήσεις) are more easily recognized. They are attuned to each
other. Therefore, dream communication between people who are connected to each
other and isolated from one another is a phenomenon that is called ‘dream
telepathy’.
146
It should be added here that Democritus (430-370 B.C.) was probably one of the first
Greek philosophers who advanced a physical theory of dream telepathy. He believed
that the external eidõla (εδωλα) that result from inanimate things or living beings,
travel through the air, penetrate the body-soul complex through its pores and cause
the phenomenon of dreaming, when they come up again.
147
His view of telepathy is
derived from the thesis that the eidõla projected by a living being are loaded with
information, and they carry with them not only the external physical likeness of their
source, but also the appearances (μφάσεις) of its psychic movements, wishes, morals
and emotions.
148
145
Gallop 1996, 167.
146
Frederic W. H. Myer (1843-1901), the founder of the Society for Psychical Research (1882), used
first the term ‘telepathy’ [from the Greek words ‘τῆλε’ (far off/distance) + ‘πάθος’ (feeling)].
147
Plutarch, Questiones Convivales, VIII, 10.2.735a1-735b5: φησι Δημόκριτος ἐγκαταβυσσοῦσθαι τὰ
εἴδωλα διὰ τῶν πόρων εἰς τὰ σώματα καὶ ποιεῖν τὰς κατὰ πνον ὄψεις ἐπαναφερόμενα· φοιτᾶν δὲ ταῦτα
πανταχόθεν ἀπιόντα καὶ σκευῶν καὶ ἱματίων καὶ φυτῶν, μάλιστα δὲ ζῴων ὑπὸ σάλου πολλοῦ κα θερμότητος
οὐ μόνον ἔχοντα μορφοειδεῖς τοῦ σώματος ἐκμεμαγμένας ὁμοιότητας (ὡς Ἐπίκουρος οἴεται μέχρι τούτου
Δημοκρίτῳ συνεπόμενος, ἐνταῦθα δὲ προλιπὼν τὸν λόγον), ἀλλ κα τῶν κατὰ ψυχὴν κινημάτων καὶ
βουλευμάτων ἑκάστῳ κα ἠθῶν καὶ παθῶν ἐμφάσεις ἀναλαμβάνοντα συνεφέλκεσθαι κα προσπίπτοντα
μετὰ τούτων ὥσπερ ἔμψυχα φράζειν καὶ διαγγέλλειν τοῖς ὑποδεχομένοις τὰς τῶν μεθιέντων αὐτὰ δόξας καὶ
διαλογισμοὺς καὶ ὁρμάς, ὅταν ἐνάρθρους καὶ ἀσυγχύτους φυλάττοντα προσμίξῃ τὰς εἰκόνας.
148
Cf. Dodds 1973, 118: “And Democritus Atomist theory of dreams as eidõla which continually
emanate from persons and objects, and affect the dreamer’s consciousness by penetrating the pores of
his body, is plainly an attempt to provide a mechanistic basis for the objective dream; it even preserves
Homer’s word for the objective dream-image. This theory makes explicit provision for telepathic
dreams by declaring that eidõla carry representations (ἐμφάσεις) of the mental activities of the beings
from whom they originate”.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
35
According to Tolaas and Ullman “Aristotle and Democritus made the paranormal
dream [dream telepathy] an object of scientific inquiry and postulated a physical
carrier for the information”.
149
But is dream telepathy a real phenomenon?
Scientific interest in dream telepathy began with the practice of psychoanalysis
since the late nineteenth century. Sigmund Freud was intrigued by telepathic dreams.
In 1922 he published a paper on dreams and telepathy (Traüm und Telepathie: Vortrag
in der Wiener Psychoanalytischen Vereinigung), which was written shortly after the
publication of an entire monograph about telepathic dreams by Wilhelm Stekel (Der
Telepathische Traüm). Freud believed that the telepathic occurrences during sleep must
be subject to psychoanalysis like any other psychological phenomenon. He also
referred to “the incontestable fact that sleep creates favorable conditions for
telepathy”.
150
The most famous clinical research on the possibility of dream telepathy was
conducted in the mid-´60s by researchers Montague Ullman, MD, and Stanley
Krippner, Professor of Psychology at Saybrook University, at the Dream Laboratory of
Maimonides Medical Center in Brooklyn, New York. Their researches
151
lasted more
than ten years, and “yielded statistically significant results“.
152
However, these results
have been treated with considerable skepticism by several researchers (Hansel 1989;
Marks 2000; Alcock 2003).
Experiments of dream telepathy using varying systems or mechanisms have
continued through the last decades, and some of them (Smith 2013, 17-25) were “well
designed and so need to be taken seriously”.
153
Concluding Remarks
In light of the preceding analysis, it became obvious that Aristotle explained sleep
and dreams in a rational way. As E. R. Dodds remarks, the Stageirite approaches
dreams from a scientific rather than a religious point of view, “and one may in fact
doubt whether in this matter modern science has advanced very far beyond him”.
154
He presents sleep and waking as psychophysical conditions, and recognizes, as the
final cause of sleep, the preservation of the organism. He denies the divine or
supernatural origin of dreams, and gives a physiological explanation, since he relates
the formation of dreams with the function of sensation (ασθησις), imagination
(φαντασία) and mind (νος).
149
Wolman 1979, 170.
150
Freud 1922, 219.
151
From 1964 to 1972 Ullman and Krippner conducted fifteen experiments of dream telepathy.
152
Krippner 1999, 12.
153
McNamara 2014, <http://www.psychologytoday.com/blog/dream-catcher/201404/can-our-
dreams-solve-problems-while-we-sleep>.
154
Dodds 1973, 120.
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
36
Finally, as I hope I have shown, the Stageirite was probably the first psychologist
who produced a detailed and profound analysis of sleep (πνος) and dreams
(νύπνια), and many of his observations on these phenomena have been verified by
modern and contemporary experimental research (e.g. Psychology,
Psychophysiology, Neurobiology, Cognitive Science etc.).
Acknowledgements
This paper is based on a research that has been co-financed by the European Union
(European Social Fund ESF) and Greek national funds through the Operational
Program "Education and Lifelong Learning" of the National Strategic Reference
Framework (NSRF) - Research Funding Program: THALIS UOA (2007-2013).
Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
37
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Ch. S. Papachristou Aristotle’s Theory of ‘Sleep and Dreams’
47
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Jozef Kelemen (FPF SU Opava, Czech Republic)
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Vladimír Kvasnička (FIIT STU Bratislava, Slovak Republic)
Jaroslav Novotný (FHS UK Praha, Czech Republic)
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Ján Pavlík (editor-in-chief) (VŠE Praha, Czech Republic)
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... • Sleepwalking. It is a NREM sleep disorder, which is most often seen in children aged [8][9][10][11][12], and this is because many episodes occur in infancy (e.g. the child is getting up and going to find his or her parents, or just going around In his cradle) go unnoticed. In sleepwalking, the child gets up from the bed and walks through the house, may seem uncomfortable and run around, or do simple activities that seem to be deliberate, like going to the bathroom. ...
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... However, what exactly is being restored by sleep remains unanswered. The functions of sleep have been speculated in the ancient works such as "Aristotle's Theory of 'Sleep and Dreams'" [8]. Aristotle proposed that sleep helps the body cleans its blood at the end of the day. ...
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... In fact Aristotle also recognizes that sleep comes first in the being and that wakefulness evolves later. [21] He actually says in De Anima "for both sleeping and waking presuppose the existence of soul, and of these waking corresponds to actual knowing, sleeping to knowledge possessed but not employed" (II,1, 412a23-26) [20]. Likewise in De Insomniis he refers to "those true thoughts which occur in sleep" (1.459a6-8). ...
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