Essays in Experimental Logic · John Dewey
SENSE PERCEPTION AS KNOWLEDGE
I mentioned incidentally in the first section that it is conceivable that failure to give adequate consideration to practical judgments may have a compromising effect upon the consideration of other types. I now intend to develop this remark with regard to sense perception as a form of knowledge. The topic is so bound up with a multitude of perplexing psychological and epistemological traditions that I have first to make it reasonably clear what it is and what it is not which I propose to discuss. I endeavored in an earlier series of papers[90] to point out that the question of the _material_ of sense perception is not, as such, a problem of the theory of knowledge at all, but simply a problem of the occurrence of a certain material--a problem of causal conditions and consequences. That is to say, the problem presented by an image[91] of a bent stick, or by a dream, or by "secondary" sensory qualities is properly a problem of physics--of conditions of occurrence, and not of logic, of truth or falsity, fact or fiction. That the existence of a red _quale_ is dependent upon disturbances of a certain velocity of a medium in connection with certain changes of the organism is not to be confused with the notion that red is a way of knowing, in some more or less adequate fashion, some more "real" object or else of knowing itself. The fact of causation--or functional dependence--no more makes the _quale_ an "appearance" to the mind of something more real than itself or of itself than it makes bubbles on the water a real fish transferred by some cognitive distortion into a region of appearance. With a little stretching we may use the term appearance in either case, but the term only means that the red _quale_ or the water-bubble is an _obvious_ or conspicuous thing from which we infer something else not so obvious.
This position thus freely resumed here needs to be adequately guarded on all sides. It implies that the question of the existence or presence of the _subject-matter_ of even a complex sense perception may be treated as a question of physics. It also implies that the _existence_ of a sense perception may be treated as a problem of physics. But the position is not that _all_ the problems of sense perception are thereby exhausted. There is still, on the contrary, the problem of the cognitive status of sense perception. So far from denying this fact, I mean rather to emphasize it in holding that this knowledge aspect is not to be identified--as it has been in both realistic and idealistic epistemologies--with the simple _occurrence_ of presented subject-matter and with the _occurrence_ of a perceptive act. It is often stated, for example, that primitive sense objects when they are stripped of all inferential material cannot possibly be false--but with the implication that they, therefore, must be true. Well, I meant to go this statement one better--to state that they are neither true nor false--that is, that the distinction of true-or-false is as irrelevant and inapplicable as to any other existence, as it is, say, to being more than five feet high or having a low blood pressure. This position when taken leaves over the question of sense perception as knowledge, as capable of truth or falsity. It is this question, then, which I intend to discuss in this paper.
Text from Project Gutenberg, public domain in the United States.