CONCEPT. A concept is an idea which has been formed by thinking, and which is permanently embodied in language by a word or other definite symbolic expression. There are two main differences between a concept and a percept. In the first place, the latter seems to be directly presented through the senses and does not imply any conscious reflection. And again, a percept as presented has always a par ticular individual form, while a concept is an ideal construction, and, as such, has universal significance. For example, I may perceive through my senses the particular object which I call my watch; but to form a concept of ewatcha is to think in general terms the relation of the mechanism of the parts to the purpose of the whole. The concept must also be dis tinguished from the mental image which appears in memory or imagination when the object is not directly present in sensation. The latter is always a particular psychological process, and therefore cannot adequately represent the gen eral relations of the concept. We must not con fuse the presence of images in the mind with thinking. It is true that a concept cannot be represented in terms of psychological content except by a particular image, and it probably always is represented by some such image. But the concept is a universal mode of thinking, and the psychological imagery which accompanies it is largely individual and indifferent. The uni versal relations of the concept of triangle for example, are not limited by the form of the particular figure which I represent to myself mentally, or draw upon paper, though the latter may aid me in comprehending those relations. The concept is ideal in character; it is a univer sal significance, and must never be confused with a particular psychological image.
Socrates was the first to bring this universal element of knowledge into clear light. When the Sophists pointed to the differences and vari ations of perceptions and feelings in individu als, and drew the conclusion that objective knowledge was impossible, Socrates showed that concepts which are true for all men can be discovered and defined, and that this is the true quest. of thought. Amid the flux of individual opinion, science is still possible, since it is con stituted by this system of universal concepts.
Plato and Aristotle developed further the So cratic doctrine of concepts and gave it an onto logical application. By means of the concept, the true form or permanent essence of things is said to be apprehended, as opposed to the accidental and changing appearances. The question as to the nature of the concept played an important part during the Middle Ages. (See NOMINALISM, REALISM, CONCEPTUALISM?. The view that is perhaps most commonly hel to-day regards the concept as derived by abstraction (q.v.) from perceptual experience, by selecting out what is common in a number of instances and combining these common elements into a general idea. It must not be forgotten, however, that concepts are not formed by the piecing to gether of psychologically common elements in a mechanical way, but are the products of thinking; and that thinking is itself judgment or interpretation of significance in universal terms. It is true, as Kant said, that concepts without percepts are empty; our thinking does not go on in a vacuum apart from concrete ex perience. But the concept is not universal be cause it has been compounded out of elements that are common to a number of objects, but because it is the mind's expression in terms of ideal significance. Concepts, however, can attain to any degree of elaboration only through the aid of language. The relation between thought and the words which express it is of the closest and most intimate kind. The word sums up in itself the results of the conceptualizing process, thus giving to it a reality and per manence which make progress possible. It is through learning the words of a language that we are able to share in the concepts of other men and other generations. Language is thus a permanent record of thought's achievements and its development is not something external to the evolution of thinking, but in one aspect may be said to be a different side of the same process. The concept then cannot be defined apart from its expression in language; for this expression is no mere external and accidental feature of the idea, but is organically and necessarily connected with it.