Essays in Experimental Logic · John Dewey
II
So far as I can see, the pronounced tendency to regard the perceived object as itself the object of a peculiar kind of knowledge instead of as a term in knowledge of the practical kind has two causes. One is the confirmed habit of neglecting the wide scope and import of practical judgments. This leads to overlooking the responsive act as the other term indicated by the perception, and to taking the perceived object as the whole of the situation just by itself. The other cause is the fact that because perceived objects are constantly employed as evidence of what is to be done--or how to do something--they themselves become the objects of prolonged and careful scrutiny. We pass naturally and inevitably from recognition to _observation_. Inference will usually take care of itself if the datum is properly determined. At the present day, a skilled physician will have little difficulty in inferring typhoid instead of malaria from certain symptoms provided he can make certain observations--that is, secure certain data from which to infer. The labor of intelligence is thus transferred from inference to the determination of data, the data being determined, however, in the interests of inference and as parts of an inference.
At this point, a significant complication enters in. The ordinary assumption in the discussion of the relation of perceived objects to knowledge is that "the" object--the real object--of knowledge in perception is the thing which _caused_ the qualities which are given. It is assumed, that is, that the other term of a proposition in which a sense datum is one term must be the thing which produced it. Since this producing object does not for the most part appear in ordinary sense perception, we have on our hands perception as an epistemological problem--the relation of an appearance to some reality which it, somehow, conceals rather than indicates. Hence also the difficulties of "reconciling" scientific knowledge in physics where these causes are the terms of the propositions with "empirical" or sense perception knowledge where they do not even appear. Here is where the primary advantage of recognizing that ordinary sense perceptions are forms of practical judgment comes in. In practical judgments, the other term is as open and aboveboard as is the sensory quality: it is the thing to be done, the response to be selected. To borrow an illustration of Professor Woodbridge's: A certain sound indicates to the mother that her baby needs attention. If she turns out to be in error, it is not because sound ought to mean so many vibrations of the air, and as matter of fact doesn't even suggest air vibrations, but because there is wrong inference as to the act to be performed.
I imagine that if error never occurred in inferences of this practical sort the human race would have gone on quite contented with them. However that may be, errors _do_ occur and the endeavor to control inference as to consequences (so as to reduce their likelihood of error) leads to propositions where the knowledge-object of the perceived thing is not something to be done, but the cause which produced it. The mother finds her baby peacefully sleeping and says the baby didn't _make_ the noise. She investigates and decides a swinging door _made_ it. Instead of inferring a consequence, she infers a cause. If she had identified the noise in the first place, she would have concluded that the hinges needed oiling.
Now where does the argument stand? The proper control of inference in specific cases is found (_a_) to lie in the proper identification of the datum. If the perception is of a certain kind, the inference takes place as a matter of course; or else inference can be suspended until more adequate data are found, and thus error is avoided even if truth be not found. Furthermore (_b_) it is discovered that the most effective way of identifying datum (and securing adequate data) is by inference to its cause. The mother stops short with the baby and the door as causes. But the same motives which made her transfer her inference from consequences to conditions are the motives which lead others to inferring from sounds to vibrations of air. Hence our scientific propositions about sensory data. They are not, as such, about things to do, but about things which have been done, have happened--"facts." But they have reference, nevertheless, to inferences regarding consequences to be effected. They are the means of securing data which will prevent errors which would otherwise occur, and which facilitate an entirely new crop of inferences as to possibilities--means and ends--of action. That scientific men should be conscious of this reference or even interested in it is not at all necessary, for I am talking about the logic of propositions, not about biography nor psychology. If I reverted to psychology, it would be to point out that there is no reason in the world why the practical activity of some men should not be predominantly directed into the pursuits connected with discovery. The extent in which they actually are so directed depends upon social conditions.
Text from Project Gutenberg, public domain in the United States.