Aristotle · a new plain-English translation from the original language
1| After this we must inquire about the dream, and first, to which part of the soul it belongs, and whether this affection belongs to the intellectual part or to the perceptual part; for it is only by these that we come to know anything among the things in us. Now if the use of sight is seeing, and of hearing is hearing, and in general the use of perception is perceiving, and if some things are common to the senses, such as shape and magnitude and motion and the like, while others are proper to each, such as color, sound, flavor, and if all these are unable to see while their eyes are shut and while they are asleep, and likewise for the rest of the senses, it is clear that we perceive nothing at all in sleep. It is not, then, by perception that we perceive the dream. But neither is it by opinion. For we say not merely that the thing approaching is a man or a horse, but also that it is white or beautiful; and about these things opinion apart from perception would assert nothing, either truly or falsely. But in sleep it happens that the soul does this; for we seem to see alike both that the approaching thing is a man and that it is white. Further, alongside the dream we also think of something else, just as when perceiving something while awake; for about the thing we perceive we often also think something further. So too in sleep, alongside the images, we sometimes think of other things as well.
2| This would become apparent to anyone who paid attention and tried, on getting up, to remember. And indeed some have already had dreams of the following sort: those who, following a rule of the art of memory, are in the habit of setting the objects proposed to them in a fixed place. For it often happens to them that, apart from the dream, some other image places itself before their eyes in that place. So it is clear both that not every image occurring in sleep is a dream, and that what we think we do so by opinion. And this much at least is clear about all these cases: that it is the same thing by which we are deceived while awake in illnesses that produces this affection in sleep as well. And even to those who are healthy and know better, the sun nonetheless appears a foot across. But whether the imaginative part of the soul is the same as the perceptual part or different, none the less it does not come about apart from seeing and perceiving something; for to see amiss and to hear amiss belong to one who is truly seeing and truly hearing something, though not the thing he supposes. But in sleep it is assumed that one sees nothing and hears nothing and perceives nothing at all. Is it, then, that seeing nothing is true, but that the sense-faculty's being affected in no way is not true, but rather it is possible that sight too is affected in some way, and the other senses as well, and that each of these, as when one is awake, does in some way impinge upon the sense, yet not in the way it does when one is awake?
3| And sometimes opinion says that what is seen is false, just as when we are awake, while sometimes it is held fast and follows the image. That this affection, then, which we call dreaming, does not belong to the part that forms opinion, nor to the part that thinks discursively, is evident. But neither does it belong, without qualification, to the perceiving part; for then one would be seeing and hearing without qualification. But how then, and in what manner, must be examined. Let it be assumed, as is indeed evident, that the affection belongs to the perceptual faculty, if indeed sleep does too; for it is not that sleep belongs to one animal and dreaming to another, but to the same one. And since imagination has been discussed in the treatise on the soul, and the imaginative faculty is the same as the perceptual faculty, though what it is for something to be the imaginative faculty and to be the perceptual faculty differ, and imagination is the motion produced by perception when in actuality, while the dream appears to be some sort of image (for we call an image occurring in sleep a dream, whether it occurs simply or in some qualified way), it is clear that dreaming belongs to the perceptual faculty, and belongs to it insofar as it is the imaginative faculty.
4| What the dream is and how it comes about we may best consider from what happens in connection with sleep. For the objects of perception, in respect of each sense-organ, produce perception in us, and the affection produced by them is present not only in the sense-organs while the acts of perceiving are in operation, but also once they have departed. For the affection in these cases seems to be much like that in things carried along. For in the case of things carried along, motion continues even after the thing that set it moving is no longer in contact; for what set it moving moved some air, and this in turn, being moved, moves another portion. And in this way, until it comes to rest, the motion continues both in air and in liquids. And the same must be supposed to hold for alteration too; for what has been heated by something hot heats what is next to it, and this transmits the heat onward as far as the starting point. So too with that in which perceiving occurs: since actual perception is a kind of alteration, this same thing must happen there as well. Hence the affection exists not only in the sense-organs while they are perceiving, but also once they have ceased, and both deep within and on the surface. This becomes evident whenever we go on perceiving something continuously; for when we shift the perception elsewhere, the affection still follows, as, for example, in passing from the sun into darkness;
5| for it happens that we see nothing, because of the motion still remaining in the eyes from the light. And if we look for a long time at one color, whether white or greenish-yellow, whatever we then turn our sight to appears of that same color. And if, after looking at the sun or some other bright object, we shut our eyes and then watch carefully, it appears directly in the line of sight in which the sight happens to be looking, first of that same color, then it changes to crimson, then to purple, until it arrives at black and vanishes. And the appearances coming from moving things also change, for example from rivers, and most of all from those flowing most swiftly; for things at rest then appear to be moving. And people become hard of hearing from great noises and lose their sense of smell from strong odors, and similarly with the other senses. These things, then, clearly happen in this way. And as a sign that the sense-organs perceive quickly and even the slightest difference, there is what happens with mirrors, about which too, if one applied one's mind and looked into it, one would raise a puzzle. And at the same time it is clear from this very fact that, just as sight is affected, so too it does something. For in mirrors that are extremely clean, whenever women who are having their monthly period look into the mirror, there occurs on the surface of the mirror something like a bloody cloud;
6| and if the mirror is new, it is not easy to wipe off such a stain, but if it is old, easier. The cause, as we said, is that sight is not only affected in some way by the air, but also does something and moves it, just as bright objects do; for sight too belongs to the class of bright things and things possessing color. The eyes, then, are reasonably affected when the monthly period occurs, just as any other part of the body is, for they too happen by nature to be full of veins. Hence, when the monthly discharge occurs, on account of the disturbance and blood-inflammation, the difference in the eyes is to us imperceptible, but it is present nonetheless (for semen and the menstrual discharge are of the same nature), and the air is moved by them, and this air, being continuous with the air upon the mirrors, it makes qualified in some way, of the same sort as it itself is affected; and this air affects the surface of the mirror. And just as, among garments, the cleanest are stained the quickest, for what is exactly clean shows clearly whatever it receives, and especially the smallest motions. And bronze, because it is smooth, perceives any touch whatsoever most readily (one must conceive of the air's contact as a kind of rubbing, and as a wiping and a washing off), while because it is clean it becomes evident, however slight the motion may be.
7| The reason that the mark does not quickly go away from new mirrors is that they are clean and smooth: for it sinks through such mirrors both to a depth and in every direction — through their being clean, to a depth, and through their being smooth, in every direction. But in old mirrors it does not remain, because the stain does not sink in the same way but more superficially. It is clear from this both that motion arises even from small differences, that perception is quick, and further that the sense-organ of colors not only is affected but also acts back. What happens with wines and with perfume-making bears witness to what has been said. For prepared oil quickly takes on the smells of things nearby, and wines undergo this same thing: for they take up smells not only from what is thrown in or mixed in, but also from things placed near the vessels, or growing near them. For the inquiry from the beginning, let one thing be laid down — which is clear from what has been said — that even when the sensible object from outside has departed, the sense-impressions remain, being perceptible; and besides this, that we are easily deceived about our perceptions when we are in the grip of emotions, different people in different ones, for instance the coward in fear, the person in love in love, so that from a small resemblance the one seems to see enemies, the other the beloved;
8| and the more emotional a person is, the more easily this appears to him from a slighter resemblance. In the same way, in fits of anger and in all appetites, everyone becomes easy to deceive, and more so the more they are in the grip of these emotions. That is why to people with fevers, animals sometimes appear on the walls, composed from a slight resemblance of the lines. And these things sometimes intensify along with the emotions to such a degree that, if the sufferers are not very ill, they do not fail to notice that it is false, but if the affliction is greater, they are actually moved toward these appearances. The cause of this happening is that the ruling faculty and the faculty by which images arise do not judge by the same power. A sign of this is that the sun appears a foot across, yet something else often contradicts this appearance. And by the crossing of the fingers, one thing appears as two, yet all the same we do not say it is two: for sight has more authority than touch. But if touch alone were operating, we would in fact judge the one to be two. The cause of being deceived is that something appears to be moving not only when the sensible object is moving, but also when the perception itself is moving, if it moves in the same way as it does under the action of the sensible object;
9| I mean, for example, that the land seems to those sailing to be moving, because their sight is being moved by something else.
10| From this it is clear that it is not only in waking people that the motions arising from sense-impressions occur — both those coming from outside and those already present from within the body — but also when this affection called sleep occurs, and indeed they appear more then. For by day they are driven out while the senses and the intellect are active, and they disappear the way a small fire does beside a much greater one, and small pains and pleasures beside great ones; but once these have ceased, even the small ones rise to the surface. At night, because of the inactivity of the particular senses and their inability to be active, since the ebb of heat occurs from outside inward, the motions are carried down to the origin of perception and become apparent as the disturbance subsides. One should suppose that, just as small eddies form in rivers, so each motion occurs continuously, often remaining similar, but often breaking up into other shapes because of the counter-current. That is why, after eating, and altogether in the very young, such as small children, dreams do not occur: for the motion is too great, on account of the heat coming from the food. So just as in a liquid, if someone stirs it violently, sometimes no image appears at all, sometimes it appears but altogether distorted, so that it appears other than what it is, but once the liquid has settled the images are clear and plain — so too in sleep, the images and the remaining motions that result from sense-impressions sometimes are altogether obliterated because the motion just mentioned is greater, and sometimes the visions appear disturbed and monstrous, and the dreams are not vigorous, as with melancholics, feverish people, and the drunk;
11| for all such conditions, being full of breath, produce much motion and disturbance. But when the blood settles and is separated out in blooded animals, the motion of the sense-impressions coming from each of the sense-organs is preserved and makes the dreams vigorous, and makes it appear and seem, through what is carried down from sight, that one sees, and through what comes from hearing, that one hears. And likewise from the other sense-organs as well: for because the motion arrives there at the origin, a person even while awake seems to see and hear and perceive; and because sight sometimes seems to move though it is not moving, we say we see, and because touch reports two motions, the one thing seems to be two. For in general, the origin declares what comes from each sense, unless another, more authoritative sense contradicts it. So the appearance occurs in every case, but what appears is not believed in every case, but only if the discriminating faculty is held fast or is not moved with its own proper motion. And just as we said that different people are easily deceived through different affections, so too the sleeper, because of sleep and because the sense-organs are in motion and the other things that happen concerning perception, is easily deceived, so that whatever has a slight resemblance to that thing appears to be that thing.
12| For when a person sleeps, as most of the blood descends to the origin, the motions present within it descend along with it, some potentially, some actually. And they stand in such relation to one another that in this motion, this particular one will rise to the surface out of it, but if this one perishes, that one will. And they stand toward one another just like the little modeled frogs that rise up in water as the salt dissolves. In this way they are present potentially, and when what restrains them is relaxed they become actual; and being set loose in the small amount of blood remaining in the sense-organs, they move, bearing a resemblance like the shapes in the clouds, which people liken to men and centaurs, changing rapidly. Each of these, as has been said, is a remnant of the sense-impression that occurred in actuality; and when the true sense-impression has departed, the remnant remains present, and it is true to say that it is such as Coriscus, but it is not Coriscus. When the person was actually perceiving, the ruling and discriminating faculty did not call it Coriscus, but called that person the real Coriscus on account of this true perception. But this faculty, which does perceive it, says this, that it is Coriscus, provided it is not entirely held fast by the blood; as though it were not perceiving this, it is moved by the motions in the sense-organs. And the resembling thing seems to itself to be the true one. And so great is the power of sleep that it makes this go unnoticed.
13| So then, just as, if someone did not notice a finger being placed beneath his eye, the one thing would not only appear but would also be believed to be two, whereas if he did notice it, it would appear so but not be believed — so too in sleep: if the sleeper perceives that he is asleep, and perceives the affection in which the perception belonging to the sleep-state consists, the image appears, but something within him says that it appears to be Coriscus but is not Coriscus (for often, while a person is asleep, something in the soul says that what appears is a dream); but if he does not notice that he is asleep, nothing contradicts the appearance. That we speak truly, and that there are image-producing motions in the sense-organs, is clear if one pays attention and tries to remember what we experience while dropping off to sleep and while waking up: for sometimes a person, on waking, will catch the images that appeared to him while asleep as being motions present in the sense-organs; for in some young people, even when they are wide awake, if it is dark, many moving images appear to them, so that they often cover their heads out of fear. From all this one must conclude that a dream is indeed some sort of image occurring in sleep; for the images just mentioned are not dreams, nor is anything else that appears when the senses have been released from their normal function;
14| Nor is every image occurring in sleep a dream. For to begin with, it happens to some people that they perceive in some way sounds, light, taste, and touch, though weakly and as if from a distance; for already, while asleep, glancing dimly, they would faintly see the light of the lamp as they were sleeping, or so they thought, and on waking immediately recognized it as the lamp's; and hearing the voice of cocks and dogs faintly, on waking they recognized it clearly. Some even answer when questioned; for it is possible that, while strictly one of the two states, waking or sleeping, holds, the other holds too in some way. None of these cases should be called a dream. Nor should the true thoughts that occur in sleep alongside the images be called dreams. But the image that arises from the motion of the sense-impressions, when this occurs in sleep, insofar as one is asleep, this is a dream. Now it has happened to some people that they have seen no dream at all in their whole life. Such a thing is rare, but it does happen. For some it lasted their whole life through; but for others a dream came only when they had advanced far in age, having seen none before. The cause of its not occurring should be thought of as something similar to this: dreams do not occur to people either just after eating or to infants. For in those whose nature is so constituted that a great deal of exhalation rises to the upper region, and this, falling back down again, produces a large amount of motion, it stands to reason that no image appears to them.
15| As age advances, it is nothing strange for a dream to appear; for when some change occurs, whether by way of age or by way of an affection, this reversal must necessarily come about.