ON SLEEP AND SLEEPLESSNESS
by Aristotle
350 BC
Isaac Newton (1642-1727)
Engelsk fysiker og matematiker. Newton var den ledende skikkelse i den
videnskabelige revolution i 1600-tallet. På baggrund av hans opdagelse av de tre
bevægelseslove lykkedes det ham at formulere loven om universel tyngdekraft (senere i
begyndelsen af dette århundrede modbevist af Arne Gabs i Danmark. Inden
matematikken var han den første til at formulere regning med uendelige store og
uendelige små størrelser. Newtons værk Principia Mathematica fra 1687 er en af de vigtigste
enkeltværker i hele den moderne videnskabshistorie.
John Locke (1632-1704)
Engelsk filosof som indførte den nye tids tanker både i England og Frankrig.
Hans tænkning var også en kilde til stor inspiration, da den amerikanske grundlov skulle
skrives. Han er kendt som den første store filosof i den engelske empiristiske
(erfaringsbaserede) tradition. Hovedbudskabet er at mennesket aldrig kan opnå sikker
viden om selve virkeligheden, og at det ikke findes «medfødte ideer». Vort sind er fra
fødselen som en ubeskrevet tavle («tabula rasa») og det er gennem erfaringen vi lærer alt
det, vi ved, eller tror vi ved, om virkeligheden. (Sammenlign med Karl Raimund Poppers
udsagn: Vi ved ikke – vi formoder).
Locke var også en betydelig pædagog. Han mener at den bedste moralske opdragelse et
barn kan få er at have forældre som går foran med et godt eksempel på mådehold. At gå
foran med det gode eksempel er langt bedre end at lave regler og forskrifter. Locke
lægger også vægt på opmuntring af børns naturlige anlæg ( sammenlign med hvad
filosofi for børn plæderer for) og at børn og forældre skal udvikle venskab indbyrdes..
René Descartes (1596-1650)
Fransk filosof, matematiker og videnskabsmand særlig kendt for sin metodiske
tvivl og for sin dualisme. Den metodiske tvivl gik ud på at tvivle på så meget, som det var
muligt at tvivle på for dermed at nå frem til noget, som var absolut sikkert. Han stillede
derfor systematisk tvivl ved alt: kirkelige udsagn, lover og regler, alt vi kan opfatte med
sanserne, fornuftens konklusioner. Etter denne proces er der bare en ting som ikke kan
betvivles, mente han, nemlig at når jeg tænker, så eksisterer jeg: «Jeg tænker, derfor er jeg»
(Cogito ergo sum).
Descartes udviklede også en strengt dualistisk filosofi hvor han skelnede mellem bevidsthed
(ånd, sjæl) og materie. F.eks. består mennesket både af sjæl (bevidsthed) og krop (materie).
Dyrene, derimod, har kun krop, ingen sjæl. Når dyr skriger (af smerte), er det derfor ikke
fordi det lider (lide kan kun et væsen med bevidsthed gøre), men fordi der er «kludder i
maskineriet». Descartes regnes som den moderne filosofis far.
Blaise Pascal (1623-1662)
Fransk matematiker, fysiker, filosof og forfatter. Pascal var katolik og hævdede
en lære om at vi kan erfare Gud gennem vores hjerter, ikke gennem fornuften som andre
filosofer på hans tid mente (f.eks. Descartes). Inden matematikken lagde han grundlaget
for den moderne lære om sandsynlighed. Inden fysikken formulerede han det som senere
skulle blive kendt som Pascals tryklov.
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Part 1
WITH regard to sleep and waking, we must consider what they are:
whether they are peculiar to soul or to body, or common to both; and
if common, to what part of soul or body they appertain: further, from
what cause it arises that they are attributes of animals, and whether
all animals share in them both, or some partake of the one only,
others of the other only, or some partake of neither and some of both.
Further, in addition to these questions, we must also inquire what the
dream is, and from what cause sleepers sometimes dream, and sometimes
do not; or whether the truth is that sleepers always dream but do not
always remember (their dream); and if this occurs, what its
explanation is.
Again, [we must inquire] whether it is possible or not to foresee the
future (in dreams), and if it be possible, in what manner; further,
whether, supposing it possible, it extends only to things to be
accomplished by the agency of Man, or to those also of which the cause
lies in supra-human agency, and which result from the workings of
Nature, or of Spontaneity.
First, then, this much is clear, that waking and sleep appertain to
the same part of an animal, inasmuch as they are opposites, and sleep
is evidently a privation of waking. For contraries, in natural as well
as in all other matters, are seen always to present themselves in the
same subject, and to be affections of the same: examples are-health
and sickness, beauty and ugliness, strength and weakness, sight and
blindness, hearing and deafness. This is also clear from the following
considerations. The criterion by which we know the waking person to be
awake is identical with that by which we know the sleeper to be
asleep; for we assume that one who is exercising sense-perception is
awake, and that every one who is awake perceives either some external
movement or else some movement in his own consciousness. If waking,
then, consists in nothing else than the exercise of sense-perception,
the inference is clear, that the organ, in virtue of which animals
perceive, is that by which they wake, when they are awake, or sleep,
when they are awake, or sleep, when they are asleep.
But since the exercise of sense-perception does not belong to soul or
body exclusively, then (since the subject of actuality is in every
case identical with that of potentiality, and what is called sense-
perception, as actuality, is a movement of the soul through the body)
it is clear that its affection is not an affection of soul
exclusively, and that a soulless body has not the potentiality of
perception. [Thus sleep and waking are not attributes of pure
intelligence, on the one hand, or of inanimate bodies, on the other.]
Now, whereas we have already elsewhere distinguished what are called
the parts of the soul, and whereas the nutrient is, in all living
bodies, capable of existing without the other parts, while none of the
others can exist without the nutrient; it is clear that sleep and
waking are not affections of such living things as partake only of
growth and decay, e.g. not of plants, because these have not the
faculty of sense-perception, whether or not this be capable of
separate existence; in its potentiality, indeed, and in its
relationships, it is separable.
Likewise it is clear that [of those which either sleep or wake] there
is no animal which is always awake or always asleep, but that both
these affections belong [alternately] to the same animals. For if
there be an animal not endued with sense-perception, it is impossible
that this should either sleep or wake; since both these are affections
of the activity of the primary faculty of sense-perception. But it is
equally impossible also that either of these two affections should
perpetually attach itself to the same animal, e.g. that some species
of animal should be always asleep or always awake, without
intermission; for all organs which have a natural function must lose
power when they work beyond the natural time-limit of their working
period; for instance, the eyes [must lose power] from [too long
continued] seeing, and must give it up; and so it is with the hand and
every other member which has a function. Now, if sense-perception is
the function of a special organ, this also, if it continues perceiving
beyond the appointed time-limit of its continuous working period, will
lose its power, and will do its work no longer. Accordingly, if the
waking period is determined by this fact, that in it sense-perception
is free; if in the case of some contraries one of the two must be
present, while in the case of others this is not necessary; if waking
is the contrary of sleeping, and one of these two must be present to
every animal: it must follow that the state of sleeping is necessary.
Finally, if such affection is Sleep, and this is a state of
powerlessness arising from excess of waking, and excess of waking is
in its origin sometimes morbid, sometimes not, so that the
powerlessness or dissolution of activity will be so or not; it is
inevitable that every creature which wakes must also be capable of
sleeping, since it is impossible that it should continue actualizing
its powers perpetually.
So, also, it is impossible for any animal to continue always sleeping.
For sleep is an affection of the organ of sense-perception--a sort of
tie or inhibition of function imposed on it, so that every creature
that sleeps must needs have the organ of sense-perception. Now, that
alone which is capable of sense-perception in actuality has the
faculty of sense-perception; but to realize this faculty, in the
proper and unqualified sense, is impossible while one is asleep. All
sleep, therefore, must be susceptible of awakening. Accordingly,
almost all other animals are clearly observed to partake in sleep,
whether they are aquatic, aerial, or terrestrial, since fishes of all
kinds, and molluscs, as well as all others which have eyes, have been
seen sleeping. 'Hard-eyed' creatures and insects manifestly assume the
posture of sleep; but the sleep of all such creatures is of brief
duration, so that often it might well baffle one's observation to
decide whether they sleep or not. Of testaceous animals, on the
contrary, no direct sensible evidence is as yet forthcoming to
determine whether they sleep, but if the above reasoning be convincing
to any one, he who follows it will admit this [viz. that they do so.]
That, therefore, all animals sleep may be gathered from these
considerations. For an animal is defined as such by its possessing
sense-perception; and we assert that sleep is, in a certain way, an
inhibition of function, or, as it were, a tie, imposed on sense-
perception, while its loosening or remission constitutes the being
awake. But no plant can partake in either of these affections, for
without sense-perception there is neither sleeping nor waking. But
creatures which have sense-perception have likewise the feeling of
pain and pleasure, while those which have these have appetite as well;
but plants have none of these affections. A mark of this is that the
nutrient part does its own work better when (the animal) is asleep
than when it is awake. Nutrition and growth are then especially
promoted, a fact which implies that creatures do not need sense-
perception to assist these processes.
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Part 2
We must now proceed to inquire into the cause why one sleeps and
wakes, and into the particular nature of the sense-perception, or
sense-perceptions, if there be several, on which these affections
depend. Since, then, some animals possess all the modes of sense-
perception, and some not all, not, for example, sight, while all
possess touch and taste, except such animals as are imperfectly
developed, a class of which we have already treated in our work on the
soul; and since an animal when asleep is unable to exercise, in the
simple sense any particular sensory faculty whatever, it follows that
in the state called sleep the same affection must extend to all the
special senses; because, if it attaches itself to one of them but not
to another, then an animal while asleep may perceive with the latter;
but this is impossible.
Now, since every sense has something peculiar, and also something
common; peculiar, as, e.g. seeing is to the sense of sight, hearing to
the auditory sense, and so on with the other senses severally; while
all are accompanied by a common power, in virtue whereof a person
perceives that he sees or hears (for, assuredly, it is not by the
special sense of sight that one sees that he sees; and it is not by
mere taste, or sight, or both together that one discerns, and has the
faculty of discerning, that sweet things are different from white
things, but by a faculty connected in common with all the organs of
sense; for there is one sensory function, and the controlling sensory
faculty is one, though differing as a faculty of perception in
relation to each genus of sensibles, e.g. sound or colour); and since
this [common sensory activity] subsists in association chiefly with
the faculty of touch (for this can exist apart from all the other
organs of sense, but none of them can exist apart from it-a subject of
which we have treated in our speculations concerning the Soul); it is
therefore evident that waking and sleeping are an affection of this
[common and controlling organ of sense-perception]. This explains why
they belong to all animals, for touch [with which this common organ is
chiefly connected], alone, [is common] to all [animals].
For if sleeping were caused by the special senses having each and all
undergone some affection, it would be strange that these senses, for
which it is neither necessary nor in a manner possible to realize
their powers simultaneously, should necessarily all go idle and become
motionless simultaneously. For the contrary experience, viz. that they
should not go to rest altogether, would have been more reasonably
anticipated. But, according to the explanation just given, all is
quite clear regarding those also. For, when the sense organ which
controls all the others, and to which all the others are tributary,
has been in some way affected, that these others should be all
affected at the same time is inevitable, whereas, if one of the
tributaries becomes powerless, that the controlling organ should also
become powerless need in no wise follow.
It is indeed evident from many considerations that sleep does not
consist in the mere fact that the special senses do not function or
that one does not employ them; and that it does not consist merely in
an inability to exercise the sense-perceptions; for such is what
happens in cases of swooning. A swoon means just such impotence of
perception, and certain other cases of unconsciousness also are of
this nature. Moreover, persons who have the bloodvessels in the neck
compressed become insensible. But sleep supervenes when such
incapacity of exercise has neither arisen in some casual organ of
sense, nor from some chance cause, but when, as has been just stated,
it has its seat in the primary organ with which one perceives objects
in general. For when this has become powerless all the other sensory
organs also must lack power to perceive; but when one of them has
become powerless, it is not necessary for this also to lose its power.
We must next state the cause to which it is due, and its quality as an
affection. Now, since there are several types of cause (for we assign
equally the 'final', the 'efficient', the 'material', and the 'formal'
as causes), in the first place, then, as we assert that Nature
operates for the sake of an end, and that this end is a good; and that
to every creature which is endowed by nature with the power to move,
but cannot with pleasure to itself move always and continuously, rest
is necessary and beneficial; and since, taught by experience, men
apply to sleep this metaphorical term, calling it a 'rest' [from the
strain of movement implied in sense-perception]: we conclude that its
end is the conservation of animals. But the waking state is for an
animal its highest end, since the exercise of sense-perception or of
thought is the highest end for all beings to which either of these
appertains; inasmuch as these are best, and the highest end is what is
best: whence it follows that sleep belongs of necessity to each
animal. I use the term 'necessity' in its conditional sense, meaning
that if an animal is to exist and have its own proper nature, it must
have certain endowments; and, if these are to belong to it, certain
others likewise must belong to it [as their condition.]
The next question to be discussed is that of the kind of movement or
action, taking place within their bodies, from which the affection of
waking or sleeping arises in animals. Now, we must assume that the
causes of this affection in all other animals are identical with, or
analogous to, those which operate in sanguineous animals; and that the
causes operating in sanguineous animals generally are identical with
those operating in man. Hence we must consider the entire subject in
the light of these instances [afforded by sanguineous animals,
especially man]. Now, it has been definitely settled already in
another work that sense-perception in animals originates ill the same
part of the organism in which movement originates. This locus of
origination is one of three determinate loci, viz. that which lies
midway between the head and the abdomen. This is sanguineous animals
is the region of the heart; for all sanguineous animals have a heart;
and from this it is that both motion and the controlling sense-
perception originate. Now, as regards movement, it is obvious that
that of breathing and of the cooling process generally takes its rise
there; and it is with a view to the conservation of the [due amount
of] heat in this part that nature has formed as she has both the
animals which respire, and those which cool themselves by moisture. Of
this [cooling process] per se we shall treat hereafter. In bloodless
animals, and insects, and such as do not respire, the 'connatural
spirit' is seen alternately puffed up and subsiding in the part which
is in them analogous [to the region of the heart in sanguineous
animals]. This is clearly observable in the holoptera [insects with
undivided wings] as wasps and bees; also in flies and such creatures.
And since to move anything, or do anything, is impossible without
strength, and holding the breath produces strength-in creatures which
inhale, the holding of that breath which comes from without, but, in
creatures which do not respire, of that which is connatural (which
explains why winged insects of the class holoptera, when they move,
are perceived to make a humming noise, due to the friction of the
connatural spirit colliding with the diaphragm); and since movement
is, in every animal, attended with some sense-perception, either
internal or external, in the primary organ of sense, [we conclude]
accordingly that if sleeping and waking are affections of this organ,
the place in which, or the organ in which, sleep and waking originate,
is self-evident [being that in which movement and sense-perception
originate, viz. the heart].
Some persons move in their sleep, and perform many acts like waking
acts, but not without a phantasm or an exercise of sense-perception;
for a dream is in a certain way a sense-impression. But of them we
have to speak later on. Why it is that persons when aroused remember
their dreams, but do not remember these acts which are like waking
acts, has been already explained in the work 'Of Problems'.
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The point for consideration next in order to the preceding is:-What
are the processes in which the affection of waking and sleeping
originates, and whence do they arise? Now, since it is when it has
sense-perception that an animal must first take food and receive
growth, and in all cases food in its ultimate form is, in sanguineous
animals, the natural substance blood, or, in bloodless animals, that
which is analogous to this; and since the veins are the place of the
blood, while the origin of these is the heart-an assertion which is
proved by anatomy-it is manifest that, when the external nutriment
enters the parts fitted for its reception, the evaporation arising
from it enters into the veins, and there, undergoing a change, is
converted into blood, and makes its way to their source [the heart].
We have treated of all this when discussing the subject of nutrition,
but must here recapitulate what was there said, in order that we may
obtain a scientific view of the beginnings of the process, and come to
know what exactly happens to the primary organ of sense-perception to
account for the occurrence of waking and sleep. For sleep, as has been
shown, is not any given impotence of the perceptive faculty; for
unconsciousness, a certain form of asphyxia, and swooning, all produce
such impotence. Moreover it is an established fact that some persons
in a profound trance have still had the imaginative faculty in play.
This last point, indeed, gives rise to a difficulty; for if it is
conceivable that one who had swooned should in this state fall asleep,
the phantasm also which then presented itself to his mind might be
regarded as a dream. Persons, too, who have fallen into a deep trance,
and have come to be regarded as dead, say many things while in this
condition. The same view, however, is to be taken of all these cases,
[i.e. that they are not cases of sleeping or dreaming].
As we observed above, sleep is not co-extensive with any and every
impotence of the perceptive faculty, but this affection is one which
arises from the evaporation attendant upon the process of nutrition.
The matter evaporated must be driven onwards to a certain point, then
turn back, and change its current to and fro, like a tide-race in a
narrow strait. Now, in every animal the hot naturally tends to move
[and carry other things] upwards, but when it has reached the parts
above [becoming cool], it turns back again, and moves downwards in a
mass. This explains why fits of drowsiness are especially apt to come
on after meals; for the matter, both the liquid and the corporeal,
which is borne upwards in a mass, is then of considerable quantity.
When, therefore, this comes to a stand it weighs a person down and
causes him to nod, but when it has actually sunk downwards, and by its
return has repulsed the hot, sleep comes on, and the animal so
affected is presently asleep. A confirmation of this appears from
considering the things which induce sleep; they all, whether potable
or edible, for instance poppy, mandragora, wine, darnel, produce a
heaviness in the head; and persons borne down [by sleepiness] and
nodding [drowsily] all seem affected in this way, i.e. they are unable
to lift up the head or the eye-lids. And it is after meals especially
that sleep comes on like this, for the evaporation from the foods
eaten is then copious. It also follows certain forms of fatigue; for
fatigue operates as a solvent, and the dissolved matter acts, if not
cold, like food prior to digestion. Moreover, some kinds of illness
have this same effect; those arising from moist and hot secretions, as
happens with fever-patients and in cases of lethargy. Extreme youth
also has this effect; infants, for example, sleep a great deal,
because of the food being all borne upwards-a mark whereof appears in
the disproportionately large size of the upper parts compared with the
lower during infancy, which is due to the fact that growth
predominates in the direction of the former. Hence also they are
subject to epileptic seizures; for sleep is like epilepsy, and, in a
sense, actually is a seizure of this sort. Accordingly, the beginning
of this malady takes place with many during sleep, and their
subsequent habitual seizures occur in sleep, not in waking hours. For
when the spirit [evaporation] moves upwards in a volume, on its return
downwards it distends the veins, and forcibly compresses the passage
through which respiration is effected. This explains why wines are not
good for infants or for wet nurses (for it makes no difference,
doubtless, whether the infants themselves, or their nurses, drink
them), but such persons should drink them [if at all] diluted with
water and in small quantity. For wine is spirituous, and of all wines
the dark more so than any other. The upper parts, in infants, are so
filled with nutriment that within five months [after birth] they do
not even turn the neck [sc. to raise the head]; for in them, as in
persons deeply intoxicated, there is ever a large quantity of moisture
ascending. It is reasonable, too, to think that this affection is the
cause of the embryo's remaining at rest in the womb at first. Also, as
a general rule, persons whose veins are inconspicuous, as well as
those who are dwarf-like, or have abnormally large heads, are addicted
to sleep. For in the former the veins are narrow, so that it is not
easy for the moisture to flow down through them; while in the case of
dwarfs and those whose heads are abnormally large, the impetus of the
evaporation upwards is excessive. Those [on the contrary] whose veins
are large are, thanks to the easy flow through the veins, not addicted
to sleep, unless, indeed, they labour under some other affection which
counteracts [this easy flow]. Nor are the 'atrabilious' addicted to
sleep, for in them the inward region is cooled so that the quantity of
evaporation in their case is not great. For this reason they have
large appetites, though spare and lean; for their bodily condition is
as if they derived no benefit from what they eat. The dark bile, too,
being itself naturally cold, cools also the nutrient tract, and the
other parts wheresoever such secretion is potentially present [i.e.
tends to be formed].
Hence it is plain from what has been said that sleep is a sort of
concentration, or natural recoil, of the hot matter inwards [towards
its centre], due to the cause above mentioned. Hence restless movement
is a marked feature in the case of a person when drowsy. But where it
[the heat in the upper and outer parts] begins to fail, he grows cool,
and owing to this cooling process his eye-lids droop. Accordingly [in
sleep] the upper and outward parts are cool, but the inward and lower,
i.e. the parts at the feet and in the interior of the body, are hot.
Yet one might found a difficulty on the facts that sleep is most
oppressive in its onset after meals, and that wine, and other such
things, though they possess heating properties, are productive of
sleep, for it is not probable that sleep should be a process of
cooling while the things that cause sleeping are themselves hot. Is
the explanation of this, then, to be found in the fact that, as the
stomach when empty is hot, while replenishment cools it by the
movement it occasions, so the passages and tracts in the head are
cooled as the 'evaporation' ascends thither? Or, as those who have hot
water poured on them feel a sudden shiver of cold, just so in the case
before us, may it be that, when the hot substance ascends, the cold
rallying to meet it cools [the aforesaid parts] deprives their native
heat of all its power, and compels it to retire? Moreover, when much
food is taken, which [i.e. the nutrient evaporation from which] the
hot substance carries upwards, this latter, like a fire when fresh
logs are laid upon it, is itself cooled, until the food has been
digested.
For, as has been observed elsewhere, sleep comes on when the corporeal
element [in the 'evaporation'] conveyed upwards by the hot, along the
veins, to the head. But when that which has been thus carried up can
no longer ascend, but is too great in quantity [to do so], it forces
the hot back again and flows downwards. Hence it is that men sink down
[as they do in sleep] when the heat which tends to keep them erect
(man alone, among animals, being naturally erect) is withdrawn; and
this, when it befalls them, causes unconsciousness, and afterwards
phantasy.
Or are the solutions thus proposed barely conceivable accounts of the
refrigeration which takes place, while, as a matter of fact, the
region of the brain is, as stated elsewhere, the main determinant of
the matter? For the brain, or in creatures without a brain that which
corresponds to it, is of all parts of the body the coolest. Therefore,
as moisture turned into vapour by the sun's heat is, when it has
ascended to the upper regions, cooled by the coldness of the latter,
and becoming condensed, is carried downwards, and turned into water
once more; just so the excrementitious evaporation, when carried up by
the heat to the region of the brain, is condensed into a 'phlegm'
(which explains why catarrhs are seen to proceed from the head); while
that evaporation which is nutrient and not unwholesome, becoming
condensed, descends and cools the hot. The tenuity or narrowness of
the veins about the brain itself contributes to its being kept cool,
and to its not readily admitting the evaporation. This, then, is a
sufficient explanation of the cooling which takes place, despite the
fact that the evaporation is exceedingly hot.
A person awakes from sleep when digestion is completed: when the heat,
which had been previously forced together in large quantity within a
small compass from out the surrounding part, has once more prevailed,
and when a separation has been effected between the more corporeal and
the purer blood. The finest and purest blood is that contained in the
head, while the thickest and most turbid is that in the lower parts.
The source of all the blood is, as has been stated both here and
elsewhere, the heart. Now of the chambers in the heart the central
communicates with each of the two others. Each of the latter again
acts as receiver from each, respectively, of the two vessels, called
the 'great' and the 'aorta'. It is in the central chamber that the
[above-mentioned] separation takes place. To go into these matters in
detail would, however, be more properly the business of a different
treatise from the present. Owing to the fact that the blood formed
after the assimilation of food is especially in need of separation,
sleep [then especially] occurs [and lasts] until the purest part of
this blood has been separated off into the upper parts of the body,
and the most turbid into the lower parts. When this has taken place
animals awake from sleep, being released from the heaviness consequent
on taking food. We have now stated the cause of sleeping, viz. that it
consists in the recoil by the corporeal element, upborne by the
connatural heat, in a mass upon the primary sense-organ; we have also
stated what sleep is, having shown that it is a seizure of the primary
sense-organ, rendering it unable to actualize its powers; arising of
necessity (for it is impossible for an animal to exist if the
conditions which render it an animal be not fulfilled), i.e. for the
sake of its conservation; since remission of movement tends to the
conservation of animals.
On sleep
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