Charles S. Peirce
Chapt. 4 (2nd draft)
MS 195 (Robin 368): Writings 3, 32-34
The memory often deceives us. We not unfrequently feel as though we had had a certain sensation or had been in a certain situation before, when it is, in fact, something entirely new. In fact, to remember is to have a certain feeling now, which makes me think that I formerly had another feeling. I do not directly know that former feeling; for it is past. I only know the feeling of remembering it; and whether I really remember it, or only seem to do so, is a matter of judgment. The only thing then of which I am immediately aware, is the feeling of the passing moment.
If I can not know even what has passed in my mind, or what will pass in it, at some other time than at present, much less can I know immediately what is external to my mind. Uninstructed persons are apt to think, that when they see a chair, for example, the whole form of that chair is impressed upon their minds at once, by an immediate perception, without any reasoning process by which the sensation is worked up, and brought into intelligible shape. But, in the first place, supposing the chair to be looked at with one eye. It is clear that the most that can be impressed upon the retina, is a flat picture of it. The vision of the chair in three dimensions, is an interpretation of this picture; but is not itself the picture. If it is looked at with both eyes, two differing pictures are made on the two retinas; and the vision of it as one will result from a still more complicated mental process. In point of fact, however, not even two dimensions are given in an immediate visual sensation; because the retina is not spread out like a sheet of paper; but consists of innumerable needle-points, which are directed towards the light, and the top of each of which is sensitive. No one of these, gives any sensation of extension, but only a flash of light without any reference to extension; therefore, all of them together give no sensation of extension, except so far as the mind is able to interpret the signs of extension which they present. It is well understood from the labors of those who have devoted themselves to the study of physiological optics, that these are but indirectly even signs of extension being primarily signs of the muscular motion which is necessary to pass from one point to another. But even if the image of the chair in its three dimensions were directly given, as it is not; still it would not be given as external to the mind. In that sensation there would be contained no decision, whether it were external or whether it were a dream; though signs might be given upon which such a decision could be based. The very fact, that dreams deceive us, shows that in the sensation itself, there is contained no judgment of the externality of the objectat least none that is of any value. A dream is distinguishable from a reality by certain signs: it is dim, and vague, and does not cohere with the rest of experience, and it is capable of explanation by the principle of association from what we have really experienced. And the opposite characters are the signs by which we know real experiences to be real. It needs no argument to show that all that we are immediately aware of is the feeling of the passing moment. And that everything outside of that, is known by this which is the sign of it. There are some feelings which are caused by previous feelings, according to certain laws which are called the laws of the association of ideas. And these are the great body of what is present to the mind, and include all that we pay particular attention to, or value; because it is naturally the results of mental action that are of importance; while the feelings from which they spring, are examined into only when the mental process comes to be subjected to currents of criticism. The other class of feelings or, perhaps, we should rather say, elements of feeling, is not so explicable by the laws of association from what has gone before in the mind, but involves something altogether new. These are termed the impressions of sense; and it is very difficult, if not impossible, for us to separate these entirely from the results of that elaboration of thought to which they are immediately subjected. It may be said, therefore, that thought, as we know it, is a stream, which, as it goes on, is enlarged by new additions. And yet, all that we can distinctly trace, is. the flow; and we can not put our finger on the points at which the new matter emerges. Thus, thought, if it takes place according to that fourth method of inquiry which is termed investigation, as it does upon most subjects, and as it doubtless will come to do on all subjects, reaches at last, as we have seen, a certain definite conclusion. And according to what has been said, the whole struggle which is the motive for investigation, is towards this settled belief and nothing else. So that that to which every image and thought in our minds endeavors to conform, and which it strives to represent, is nothing else than what will be believed in the final upshot of inquiry. On the other hand, if we mount the stream of thought instead of descending it, we see each thought caused by previous thought, until at last we reach the original sensations, which it is supposed themselves are caused by something external. In using the word "supposed," I do not wish to imply that there is any room for doubt in the matter; but only that the external realities are not themselves the immediate object of thought but are only what it is necessary to suppose exist, to account for the phenomena of sensation. We find in this stream of thought, in this succession of images, a certain coherency, harmony or consistency, which can not be due entirely to the laws of association themselves; but which extends into the additions which are made to the body of our thought from without. And it is this coherency of experience which demonstrates the existence of a reality; or something permanent and fixed, to which our thought and experience, more or less perfectly, corresponds. Now we may suppose that this reality is to be found at the one or the other extremity of the stream of thought. It either lies in some external permanency, which causes the sensation; or in the fixed opinion in which the process of thought is destined to result. Let us examine these two opposite conceptions of reality. The first one is very simple and familiar and will require no explanation.