We are confronted with this alternative. Either the image has a logical function in virtue of its sense-content, or else the image functions logically merely as a symbol, the sense-content of which is a matter of complete logical indifference. According to the empiricist, the former is the case, according to the conceptualist, the latter. The empiricist would say that he needs the image to piece out the data upon which logical processes operate. Having met this need, the image is retired from active service. For the empiricist the processes of thought, observing, comparing, generalizing, etc., are as independent of the data they use as, for the conceptualist, logical meaning, reference, and "idea" are independent of the sense-content of the "image." In reality he agrees with the conceptualist in excluding the sense-content of the image from the processes of thought, and hence from the domain of logic.
From the standpoint of psychological theory the conceptualist is an improvement over the empiricist. He has gone a step farther in the analysis of thought-processes by showing that they are bound up with some kind of imagery, however irrelevant, inconsequential, and worn down the sense-quality of that imagery may be. His statement of ideas as references to reality lends itself readily, as we have seen, to the unitary conception in psychology of ideo-motor, or sensori-motor, activity. But is this where logical theory is to stop, while psychology as a study of "states of consciousness" takes up the unfinished tale and carries it forward? It seems hardly possible, unless logic is willing to give over its task of thinking about thinking.
Reduce the image to a mere symbol. Let its sense-quality be a matter of complete indifference. What have you, then, but an elementary and primitive type of reflex action? It is of no particular consequence even from what sense-organ it appears to proceed, or whether it appears to be peripherally or centrally excited. It is simply a case of feel and act; touch and go. Is this thinking? It may be regarded as either the germ or the finality of thinking, but what most of us are inclined to believe is the true subject-matter of logic is not to be limited to a simple reflex, or even to a chain of reflexes. It is something more complex, even if nothing more than an intricate tangle of chains of reflexes.
The complexity of the process called thinking does not reside alone in the instinctive or habitual reflexes involved. The more instinctive and habitual any adjustment may be, the less is it a matter of thought, as everyone knows, although its biological complexity is none the less patent to one who looks at it from the outside. The complexity of the thinking process resides in consciousness also; it resides in the imagery, the stimuli, the mere symbols, if you like, that have "come" to consciousness. As soon as the complexity begins to be felt, as soon as any discrimination whatsoever begins to be introduced or appreciated, at that instant the sense-content, the quale, of imagery begins to have a logical function. Conscious discrimination, however vague and evanescent, and the logical function of the quale of imagery are born together, unless one chooses to regard the more obvious and deliberate forms of conscious discrimination as more characteristic of a logical process. It is only as the sense-contents of various images are discriminated and compared that anything like thinking can be conceived to go on. The particular sense-content of an image, instead of being a matter of logical indifference, is the condition, the possibility, of thinking.
The conceptualist has contributed to the data of descriptive psychology by calling attention, by implication at least, to the remote and reduced character of the imagery which may characterize thinking. But it by no means follows that the more remote and reduced the sense-content of an image becomes, the less important is that sense-content for thinking, the less demand for discrimination. On the contrary, the sense-content that remains may be of supreme logical importance. It may be the quintessence of meaning. It may be the conscious factor which, when discriminated from another almost equally sublimated conscious factor, may determine a whole course of action. The delicacy and rapidity with which these reduced forms of imagery as they hover about the margin of consciousness or flit across its focus are discriminated and caught, are points in the technique of that long art of thinking, begun in early childhood. The fact that questionnaire investigations—like that of Galton's, for example—have in many instances failed to discover in the minds of scientists and advanced thinkers a rich and varied furniture of imagery does not argue the poverty of imagery in such minds; it argues, rather, a highly developed technique, a species of virtuosity, with reference to the sense-content of the types of imagery actually in use.
To push a step farther the alternative we have already stated in a preliminary way: Either the "idea," or "logical meaning," lies outside of the process of thinking, as a mere impulse or reflex; or else, in virtue of the sense-content of its "image," it enters into that conscious process of discrimination, comparison, and selection, of light and shade, of doubt and inquiry, which constitutes the evolution of a judgment, which makes the life-history of a movement of thought.