Analogous proofs will be found presently in regard to the ideas of class, force, personality and efficacy. It is even possible to ask if the idea of contradiction does not also depend upon social conditions. What makes one tend to believe this is that the empire which the idea has exercised over human thought has varied with times and societies. To-day the principle of identity dominates scientific thought; but there are vast systems of representations which have played a considerable rôle in the history of ideas where it has frequently been set aside: these are the mythologies, from the grossest up to the most reasonable.[13] There, we are continually coming upon beings which have the most contradictory attributes simultaneously, who are at the same time one and many, material and spiritual, who can divide themselves up indefinitely without losing anything of their constitution; in mythology it is an axiom that the part is worth the whole. These variations through which the rules which seem to govern our present logic have passed prove that, far from being engraven through all eternity upon the mental constitution of men, they depend, at least in part, upon factors that are historical and consequently social. We do not know exactly what they are, but we may presume that they exist.[14]
This hypothesis once admitted, the problem of knowledge is posed in new terms.
Up to the present there have been only two doctrines in the field. For some, the categories cannot be derived from experience: they are logically prior to it and condition it. They are represented as so many simple and irreducible data, imminent in the human mind by virtue of its inborn constitution. For this reason they are said to be _a priori_. Others, however, hold that they are constructed and made up of pieces and bits, and that the individual is the artisan of this construction.[15]
But each solution raises grave difficulties.
Is the empirical thesis the one adopted? Then it is necessary to deprive the categories of all their characteristic properties. As a matter of fact they are distinguished from all other knowledge by their universality and necessity. They are the most general concepts which exist, because they are applicable to all that is real, and since they are not attached to any particular object they are independent of every particular subject; they constitute the common field where all minds meet. Further, they must meet there, for reason, which is nothing more than all the fundamental categories taken together, is invested with an authority which we could not set aside if we would. When we attempt to revolt against it, and to free ourselves from some of these essential ideas, we meet with great resistances. They do not merely depend upon us, but they impose themselves upon us. Now empirical data present characteristics which are diametrically opposed to these. A sensation or an image always relies upon a determined object, or upon a collection of objects of the same sort, and expresses the momentary condition of a particular consciousness; it is essentially individual and subjective. We therefore have considerable liberty in dealing with the representations of such an origin. It is true that when our sensations are actual, they impose themselves upon us _in fact_. But _by right_ we are free to conceive them otherwise than they really are, or to represent them to ourselves as occurring in a different order from that where they are really produced. In regard to them nothing is forced upon us except as considerations of another sort intervene. Thus we find that we have here two sorts of knowledge, which are like the two opposite poles of the intelligence. Under these conditions forcing reason back upon experience causes it to disappear, for it is equivalent to reducing the universality and necessity which characterize it to pure appearance, to an illusion which may be useful practically, but which corresponds to nothing in reality; consequently it is denying all objective reality to the logical life, whose regulation and organization is the function of the categories. Classical empiricism results in irrationalism; perhaps it would even be fitting to designate it by this latter name.