IDENTITY, meaning in general the state of being the same, can be predicated properly only of individual things. The philosophical consideration of identity has been undertaken from three different points of view. Identity was thus approached as: (1) The logical law of identity; (2) the metaphysical concept of the identity of a thing; (3) the special psychological form which this concept takes in the case of a conscious being OF person.
1. There are certain very general principles exemplified in all thought, and some have sup posed the task of logic to consist merely in developing their implications. These principles are known as the law of identity, the law of contradiction and the law of excluded middle. We are concerned here only with the law of Identity ; the other laws have been named to reveal the position of this law among its cor relatives in the science of thought. The law of identity may be formulated by saying that (whatever is, is); or symbolically, that (A is A.' In other words, if we think about anything then we must think, according to the law of identity, that it is what it is. This so-called necessity of thought amounts really to the apprehension of a necessity in the being of things. The law of identity and the law of contradiction is meta physical or ontological. In the case of the former law, this is because whatever is must be determinately what it is,—that one must think it is. The law of excluded middle is so far different as a disjunctive proposition ex presses doubt, and doubt belongs to mind, not to things. Unless the primary laws of thought were laws of things as well, our thinking would be doomed by its very nature to misapprehend the nature of things.
The logical law which we are now consider ing in particular is best understood as simply the positive form of that axiom of all con sistent thinking which the law of contradiction states negatively. Thus we are reminded by the latter that a judgment cannot be now true, now false. But if true at all, it must remain true always. For if the truth of a judgment fluctuated without any change in the subject natter of such judgment, all thought would amount but to confusion. All the functions peculiar to thought receive their differentiating characteristic only through a detachment from the flow of sense-presentation and by estab lishing themselves as independent of it: the judgment presents its content as something fixed in contrast to the stream of presentations; it proclaims its connection of ideas to be some thing that does not pass away with the act of connecting them, but persists in face of all the changes of the psychical life. Thus all truth
is eternal.
2. Sir William Hamilton well observes that the identity is the relation between our cogni tions of a thing, not between things themselves. Let us consider briefly the metaphysical rela tions of the logical law of identity. It is meta physical, we said, because whatever is must be determinately what it is, that one must think it so. Owing to considerations like these, philosophers find it difficult in admitting the possibility of an absolute change —change when nothing remains the same. For in such a change one cannot say who it is that changes. In this spirit Kant remarked "only the perma nent can change." May we not suspect, how ever, that the great Konigsberg thinker here unthinkingly reifies, employing his favorite. "thing-in-ntself," synonymous with Spencer's 'absolute"? For let one ask: What is that which remains unchanged or permanent? How are we to conceive it? And how are we to conceive of the junction between the abiding nature of a "thing" and the changing states? These are very difficult questions to answer, as any perusal of Berkeley will show. For no doubt what the word "thing" conveys is a mere logical construction,— all the aspects of a 'thing" alone being real. Cognition analyses %things" into bundles of relations and all these relations together making up the thing. What appears to be the truth is that the conceptions `things" and °relations" are inventions pure and simple for describing certain parts of the whole, as well as certain interactions and interconnec tions in a world-conception. In reality there are no things. These are only actions. In the notion of "thing's" inheres the physical assump tion of a continuity. By being itself we under stand the immediacy of ceaseless change. In a hypothetical sense, continuity may be allowed to be a necessary condition if two appearances are to be classed as appearances of the same thing. By one °thing"— a "Hiffsconstruction" as it is — we mean a combination of sensible continuity and causal connection; it is a certain series, namely, those which would commonly be said to be of the thing. If the a priori belief in permanence or continuity had not existed the laws which are now formulated in terms of this belief might just as well have been formulated without it. Things are those series of aspects which obey the laws of physics.