On the other hand, things merely imagined may sometimes be very vivid and insistent. To some persons, what exists in the imagination is dim and indefinite in the extreme. Others imagine things vividly, and can describe what is present only to the imagination almost as though it were something seen. Finally, we know that an image may become so vivid and insistent as to be mistaken for an external thing. That is to say, there are such things as hallucinations.
The criterion of vividness will not, therefore, always serve to distinguish between what is given in the sense and what is only imagined. And, indeed, it becomes evident, upon reflection, that we do not actually make it our ultimate test. We may be quite willing to admit that faint sensations may come to be confused with what is imagined, with "ideas," but we always regard such a confusion as somebody"s error. We are not ready to admit that things perceived faintly are things imagined, or that vivid "ideas" are things perceived by sense.
Let us come back to the ill.u.s.trations with which we started. How do I know that I perceive the desk before me; and how do I know that, sitting here, I imagine, and do not see, the front door of the house?
My criterion is this: when I have the experience I call "seeing my desk," the bit of experience which presents itself as my desk is in a certain setting. That is to say, the desk seen must be in a certain relation to my body, and this body, as I know it, also consists of experiences. Thus, if I am to know that I see the desk, I must realize that my eyes are open, that the object is in front of me and not behind me, etc.
The desk as seen varies with the relation to the body in certain ways that we regard as natural and explicable. When I am near it, the visual experience is not just what it is when I recede from it. But how can I know that I am near the desk or far from it? What do these expressions mean? Their full meaning will become clearer in the next chapter, but here I may say that nearness and remoteness must be measured for me in experiences of some sort, or I would never know anything as near to or far from my body.
Thus, all our sensory experiences are experiences that fall into a certain system or order. It is a system which we all recognize implicitly, for we all reject as merely imaginary those experiences which lack this setting. If my eyes are shut--I am speaking now of the eyes as experienced, as felt or perceived, as given in sensation--I never say; "I see my desk," no matter how vivid the image of the object. Those who believe in "second sight" sometimes talk of seeing things not in this setting, but the very name they give to the supposed experience indicates that there is something abnormal about it. No one thinks it remarkable that I see the desk before which I perceive myself to be sitting with open eyes. Every one would think it strange if I could see and describe the table in the next room, now shut away from me. When a man thinks he hears his name p.r.o.nounced, and, turning his head, seeks in vain for the speaker, he sets his experience down as a hallucination. He says, I did not really hear that; I merely imagined it.
May one not, with open eyes, have a hallucination of vision, just as one may seem to hear one"s name p.r.o.nounced when no one is by?
Certainly. But in each case the experience may be proved to be a hallucination, nevertheless. It may be recognized that the sensory setting is incomplete, though it may not, at first, seem so. Thus the unreal object which seems to be seen may be found to be a thing that cannot be touched. Or, when one has attained to a relatively complete knowledge of the system of experiences recognized as sensory, one may make use of roundabout methods of ascertaining that the experience in question does not really have the right setting. Thus, the ghost which is seen by the terrified peasant at midnight, but which cannot be photographed, we may unhesitatingly set down as something imagined and not really seen.
All our sensations are, therefore, experiences which take their place in a certain setting. This is our ultimate criterion. We need not take the word of the philosopher for it. We need only reflect, and ask ourselves how we know that, in a given case, we are seeing or hearing or touching something, and are not merely imagining it. In every case, we shall find that we come back to the same test. In common life, we apply the test instinctively, and with little realization of what we are doing.
And if we turn to the psychologist, whose business it is to be more exact and scientific, we find that he gives us only a refinement of this same criterion. It is important to him to distinguish between what is given in sensation and what is furnished by memory or imagination, and he tells us that sensation is the result of a message conducted along a sensory nerve to the brain.
Here we see emphasized the relation to the body which has been mentioned above. If we ask the psychologist how he knows that the body he is talking about is a real body, and not merely an imagined one, he has to fall back upon the test which is common to us all. A real hand is one which we see with the eyes open, and which we touch with the other hand. If our experiences of our own body had not the setting which marks all sensory experiences, we could never say: I _perceive_ that my body is near the desk. When we call our body real, as contrasted with things imaginary, we recognize that this group of experiences belongs to the cla.s.s described; it is given in sensation, and is not merely thought of.
It will be observed that, in distinguishing between sensations and things imaginary, we never go beyond the circle of our experiences. We do not reach out to a something _beyond_ or _behind_ experiences, and say: When such a reality is present, we may affirm that we have a sensation, and when it is not, we may call the experience imaginary.
If there were such a reality as this, it would do us little good, for since it is not supposed to be perceived directly, we should have to depend upon the sensations to prove the presence of the reality, and could not turn to the reality and ask it whether we were or were not experiencing a sensation. The distinction between sensations and what is imaginary is an _observed_ distinction. It can be _proved_ that some experiences are sensory and that some are not. This means that, in drawing the distinction, we remain within the circle of our experiences.
There has been much unnecessary mystification touching this supposed reality behind experiences. In the next chapter we shall see in what senses the word "reality" may properly be used, and in what sense it may not. There is a danger in using it loosely and vaguely.
16. MAY WE CALL "THINGS" GROUPS OF SENSATIONS?--Now, the external world seems to the plain man to be directly given in his sense experiences.
He is willing to admit that the table in the next room, of which he is merely thinking, is known at one remove, so to speak. But this desk here before him: is it not known directly? Not the mental image, the mere representative, but the desk itself, a something that is physical and not mental?
And the psychologist, whatever his theory of the relation between the mind and the world, seems to support him, at least, in so far as to maintain that in sensation the external world is known as directly as it is possible for the external world to be known, and that one can get no more of it than is presented in sensation. If a sense is lacking, an aspect of the world as given is also lacking; if a sense is defective, as in the color-blind, the defect is reflected in the world upon which one gazes.
Such considerations, especially when taken together with what has been said at the close of the last section about the futility of looking for a reality behind our sensations, may easily suggest rather a startling possibility. May it not be, if we really are shut up to the circle of our experiences, that the physical things, which we have been accustomed to look upon as non-mental, are nothing more than complexes of sensations? Granted that there seems to be presented in our experience a material world as well as a mind, may it not be that this material world is a mental thing of a certain kind--a mental thing contrasted with other mental things, such as imaginary things?
This question has always been answered in the affirmative by the idealists, who claim that all existence must be regarded as psychical existence. Their doctrine we shall consider later (sections 49 and 53). It will be noticed that we seem to be back again with Professor Pearson in the last chapter.
To this question I make the following answer: In the first place, I remark that even the plain man distinguishes somehow between his sensations and external things. He thinks that he has reason to believe that things do not cease to exist when he no longer has sensations. Moreover, he believes that things do not always appear to his senses as they really are. If we tell him that his sensations _are_ the things, it shocks his common sense. He answers: Do you mean to tell me that complexes of sensation can be on a shelf or in a drawer? can be cut with a knife or broken with the hands? He feels that there must be some real distinction between sensations and the things without him.
Now, the notions of the plain man on such matters as these are not very clear, and what he says about sensations and things is not always edifying. But it is clear that he feels strongly that the man who would identify them is obliterating a distinction to which his experience testifies unequivocally. We must not hastily disregard his protest. He is sometimes right in his feeling that things are not identical, even when he cannot prove it.
In the second place, I remark that, in this instance, the plain man is in the right, and can be shown to be in the right. "Things" are not groups of sensations. The distinction between them will be explained in the next section.
17. THE DISTINCTION BETWEEN SENSATIONS AND "THINGS"--Suppose that I stand in my study and look at the fire in the grate. I am experiencing sensations, and am not busied merely with an imaginary fire. But may my whole experience of the fire be summed up as an experience of sensations and their changes? Let us see.
If I shut my eyes, the fire disappears. Does any one suppose that the fire has been annihilated? No. We say, I no longer see it, but nothing has happened to the fire.
Again, I may keep my eyes open, and simply turn my head. The fire disappears once more. Does any one suppose that my turning my head has done anything to the fire? We say unhesitatingly, my sensations have changed, but the fire has remained as it was.
Still, again, I may withdraw from the fire. Its heat seems to be diminished. Has the fire really grown less hot? And if I could withdraw to a sufficient distance, I know that the fire would appear to me smaller and less bright. Could I get far enough away to make it seem the faintest speck in the field of vision, would I be tempted to claim that the fire shrunk and grew faint merely because I walked away from it? Surely not.
Now, suppose that I stand on the same spot and look at the fire without turning my head. The stick at which I am gazing catches the flame, blazes up, turns red, and finally falls together, a little ma.s.s of gray ashes. Shall I describe this by saying that my sensations have changed, or may I say that the fire itself has changed? The plain man and the philosopher alike use the latter expression in such a case as this.
Let us take another ill.u.s.tration. I walk towards the distant house on the plain before me. What I see as my goal seems to grow larger and brighter. It does not occur to me to maintain that the house changes as I advance. But, at a given instant, changes of a different sort make their appearance. Smoke arises, and flames burst from the roof.
Now I have no hesitation in saying that changes are taking place in the house. It would seem foolish to describe the occurrence as a mere change in my sensations. Before it was my sensations that changed; now it is the house itself.
We are drawing this distinction between changes in our sensations and changes in things at every hour in the day. I cannot move without making things appear and disappear. If I wag my head, the furniture seems to dance, and I regard it as a mere seeming. I count on the clock"s going when I no longer look upon its face. It would be absurd to hold that the distinction is a mere blunder, and has no foundation in our experience. The role it plays is too important for that. If we obliterate it, the real world of material things which seems to be revealed in our experience melts into a chaos of fantastic experiences whose appearances and disappearances seem to be subject to no law.
And it is worthy of remark that it is not merely in common life that the distinction is drawn. Every man of science must give heed to it.
The psychologist does, it is true, pay much attention to sensations; but even he distinguishes between the sensations which he is studying and the material things to which he relates them, such as brains and sense-organs. And those who cultivate the physical sciences strive, when they give an account of things and their behavior, to lay before us a history of changes a.n.a.logous to the burning of the stick and of the house, excluding mere changes in sensations.
There is no physicist or botanist or zoologist who has not our common experience that things as perceived by us--our experiences of things--appear or disappear or change their character when we open or shut our eyes or move about. But nothing of all this appears in their books. What they are concerned with is things and their changes, and they do not consider such matters as these as falling within their province. If a botanist could not distinguish between the changes which take place in a plant, and the changes which take place in his sensations as he is occupied in studying the plant, but should tell us that the plant grows smaller as one recedes from it, we should set him down as weak-minded.
That the distinction is everywhere drawn, and that we must not obliterate it, is very evident. But we are in the presence of what has seemed to many men a grave difficulty. Are not things presented in our experience only as we have sensations? what is it to perceive a thing?
is it not to have sensations? how, then, _can_ we distinguish between sensations and things? We certainly do so all the time, in spite of the protest of the philosopher; but many of us do so with a haunting sense that our behavior can scarcely be justified by the reason.
Our difficulty, however, springs out of an error of our own. Grasping imperfectly the full significance of the word "sensation," we extend its use beyond what is legitimate, and we call by that name experiences which are not sensations at all. Thus the external world comes to seem to us to be not really a something contrasted with the mental, but a part of the mental world. We accord to it the attributes of the latter, and rob it of those distinguishing attributes which belong to it by right. When we have done this, we may feel impelled to say, as did Professor Pearson, that things are not really "outside" of us, as they seem to be, but are merely "projected" outside--thought of as if they were "outside." All this I must explain at length.
Let us come back to the first of the ill.u.s.trations given above, the case of the fire in my study. As I stand and look at it, what shall I call the red glow which I observe? Shall I call it a _quality of a thing_, or shall I call it a _sensation_?
To this I answer: _I may call it either the one or the other, according to its setting among other experiences_.
We have seen (section 15) that sensations and things merely imaginary are distinguished from one another by their setting. With open eyes we see things; with our eyes closed we can imagine them: we see what is before us; we imagine what lies behind our backs. If we confine our attention to the bit of experience itself, we have no means of determining whether it is sensory or imaginary. Only its setting can decide that point. Here, we have come to another distinction of much the same sort. That red glow, that bit of experience, taken by itself and abstracted from all other experiences, cannot be called either a sensation or the quality of a thing. Only its context can give us the right to call it the one or the other.
This ought to become clear when we reflect upon the ill.u.s.tration of the fire. We have seen that one whole series of changes has been unhesitatingly described as a series of changes in my sensations. Why was this? Because it was observed to depend upon changes in the relations of my body, my senses (a certain group of experiences), to the bit of experience I call the fire. Another series was described as a series of changes in the fire. Why? Because, the relation to my senses remaining unchanged, changes still took place, and had to be accounted for in other ways.
It is a matter of common knowledge that they can be accounted for in other ways. This is not a discovery of the philosopher. He can only invite us to think over the matter and see what the unlearned and the learned are doing at every moment. Sometimes they are noticing that experiences change as they turn their heads or walk toward or away from objects; sometimes they abstract from this, and consider the series of changes that take place independently of this.
That bit of experience, that red glow, is not related only to my body.
Such experiences are related also to each other; they stand in a vast independent system of relations, which, as we have seen, the man of science can study without troubling himself to consider sensations at all. This system is the external world--the external world as known or as knowable, the only external world that it means anything for us to talk about. As having its place in this system, a bit of experience is not a sensation, but is a quality or aspect of a thing.
Sensations, then, to be sensations, must be bits of experience considered in their relation to some organ of sense. They should never be confused with qualities of things, which are experiences in a different setting. It is as unpardonable to confound the two as it is to confound sensations with things imaginary.
We may not, therefore, say that "things" are groups of sensations. We may, if we please, describe them as complexes of qualities. And we may not say that the "things" we perceive are really "inside" of us and are merely "projected outside."
What can "inside" and "outside" mean? Only this. We recognize in our experience two distinct orders, the _objective order_, the system of phenomena which const.i.tutes the material world, and the _subjective order_, the order of things mental, to which belong sensations and "ideas." That is "outside" which belongs to the objective order. The word has no other meaning when used in this connection. That is "inside" which belongs to the subjective order, and is contrasted with the former.
If we deny that there is an objective order, an external world, and say that everything is "inside," we lose our distinction, and even the word "inside" becomes meaningless. It indicates no contrast. When men fall into the error of talking in this way, what they do is to _keep_ the external world and gain the distinction, and at the same time to _deny_ the existence of the world which has furnished it. In other words, they put the clerk into a telephone exchange, and then tell us that the exchange does not really exist. He is inside--of what? He is inside of nothing. Then, can he really be inside?
We see, thus, that the plain man and the man of science are quite right in accepting the external world. The objective order is known as directly as is the subjective order. Both are orders of experiences; they are open to observation, and we have, in general, little difficulty in distinguishing between them, as the ill.u.s.trations given above amply prove.
18. THE EXISTENCE OF MATERIAL THINGS.--One difficulty seems to remain and to call for a solution. We all believe that material things exist when we no longer perceive them. We believe that they existed before they came within the field of our observation.
In these positions the man of science supports us. The astronomer has no hesitation in saying that the comet, which has sailed away through s.p.a.ce, exists, and will return. The geologist describes for us the world as it was in past ages, when no eye was opened upon it.
But has it not been stated above that the material world is an order of _experiences_? and can there be such a thing as an experience that is not _experienced_ by somebody? In other words, can the world exist, except as it is _perceived to exist_?
This seeming difficulty has occasioned much trouble to philosophers in the past. Bishop Berkeley (1684-1753) said, "To exist is to be perceived." There are those who agree with him at the present day.
Their difficulty would have disappeared had they examined with sufficient care the meaning of the word "exist." We have no right to pa.s.s over the actual uses of such words, and to give them a meaning of our own. If one thing seems as certain as any other, it is that material things exist when we do not perceive them. On what ground may the philosopher combat the universal opinion, the dictum of common sense and of science? When we look into his reasonings, we find that he is influenced by the error discussed at length in the last section--he has confused the phenomena of the two orders of experience.
I have said that, when we concern ourselves with the objective order, we abstract or should abstract, from the relations which things bear to our senses. We account for phenomena by referring to other phenomena which we have reason to accept as their physical conditions or causes.