It must be clear to the careful reader of Professor Pearson's paragraphs, that he does not confine himself strictly to the world of mere "projections," to an outer world which is really inner. If he did this, the distinction between inner and outer would disappear. Let us consider for a moment the imprisoned clerk. He is in a telephone exchange, about him are wires and subscribers. He gets only sounds and must build up his whole universe of things out of sounds. Now we are supposing him to be in a telephone exchange, to be receiving messages, to be building up a world out of these messages. Do we for a moment think of him as building up, out of the messages which came along the wires, those identical wires which carried the messages and the subscribers which sent them? Never! we distinguish between the exchange, with its wires and subscribers, and the messages received and worked up into a world. In picturing to ourselves the telephone exchange, we are doing what the plain man and the psychologist do when they distinguish between mind and body—they never suppose that the messages which come through the senses are identical with the senses through which they come.
But suppose we maintain that there is no such thing as a telephone exchange, with its wires and subscribers, which is not to be found within some clerk. Suppose the real external world is something inner and only "projected" without, mistakenly supposed by the unthinking to be without. Suppose it is nonsense to speak of a wire which is not in the mind of a clerk. May we under such circumstances describe any clerk as in a telephone exchange? as receiving messages? as no nearer to his subscribers than his end of the wire? May we say that sense-impressions come flowing in to him? The whole figure of the telephone exchange becomes an absurdity when we have once placed the exchange within the clerk. Nor can we think of two clerks as connected by a wire, when it is affirmed that every wire must "really" be in some clerk.
The truth is, that, in the extracts which I have given above and in many other passages in the same volume, the real external world, the world which does not exist in the mind but without it, is much discredited, and is yet not actually discarded. The ego is placed at the brain terminals of the sensory nerves, and it receives messages which flow in; i.e. the clerk is actually placed in an exchange. That the existence of the exchange is afterward denied in so many words does not mean that it has not played and does not continue to play an important part in the thought of the author.
It is interesting to see how a man of science, whose reflections compel him to deny the existence of the external world that we all seem to perceive and that we somehow recognize as distinct from anything in our minds, is nevertheless compelled to admit the existence of this world at every turn.
But if we do admit it, what shall we make of it? Shall we deny the truth of what the psychologist has to tell us about a knowledge of things only through the sensations to which they give rise? We cannot, surely, do that. Shall we affirm that we know the external world directly, and at the same time that we do not know it directly, but only indirectly, and through the images which arise in our minds? That seems inconsistent. Certainly there is material for reflection here.
Nevertheless the more we reflect on that material, the more evident does it become that the plain man cannot be wrong in believing in the external world which seems revealed in his experiences. We find that all attempts to discredit it rest upon the implicit assumption of its existence, and fall to the ground when that existence is honestly denied. So our problem changes its form. We no longer ask: Is there an external world? but rather: What is the external world, and how does it differ from the world of mere ideas?
[1] "The Grammar of Science," 2d Ed., London, 1900, pp. 60–63.
CHAPTER IV
SENSATIONS AND "THINGS"
15. SENSE AND IMAGINATION.—Every one distinguishes between things perceived and things only imagined. With open eyes I see the desk before me; with eyes closed, I can imagine it. I lay my hand on it and feel it; I can, without laying my hand on it, imagine that I feel it. I raise my eyes, and see the pictures on the wall opposite me; I can sit here and call before my mind the image of the door by which the house is entered.
What is the difference between sense and imagination? It must be a difference of which we are all somehow conscious, for we unhesitatingly distinguish between the things we perceive and the things we merely imagine.
It is well to remember at the outset that the two classes of experiences are not wholly different. The blue color that I imagine seems blue. It does not lose this quality because it is only imaginary. The horse that I imagine seems to have four legs, like a horse perceived. As I call it before my mind, it seems as large as the real horse. Neither the color, nor the size, nor the distribution of parts, nor any other attribute of the sort appears to be different in the imaginary object from what it is in the object as given in sensation.
The two experiences are, nevertheless, not the same; and every one knows that they are not the same. One difference that roughly marks out the two classes of experiences from one another is that, as a rule, our sense-experiences are more vivid than are the images that exist in the imagination.
I say, as a rule, for we cannot always remark this difference. Sensations may be very clear and unmistakable, but they may also be very faint and indefinite. When a man lays his hand firmly on my shoulder, I may be in little doubt whether I feel a sensation or do not; but when he touches my back very lightly, I may easily be in doubt, and may ask myself in perplexity whether I have really been touched or whether I have merely imagined it. As a vessel recedes and becomes a mere speck upon the horizon, I may well wonder, before I feel sure that it is really quite out of sight, whether I still see the dim little point, or whether I merely imagine that I see it.
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 illustrations 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