We should note, however, that in the attempt thus made to undo the work of several generations Diogenes retained the principle which had wrought the mischief. We have before remarked that the germ of the Atomic philosophy was contained in the process of rarefaction and condensation. Hence, in accepting it along with the remainder of Anaximenes's theory, the fatal assumption was reinstated. It is the story of human systems in epitome. The superstructure is overthrown, and with the débris a new edifice is built upon the old foundations.
In the entire course of philosophical thought from Thales onward the suggestion of an opposition between the subject and the predicate had appeared. It has often been said that it was expressed by the search for a φύσις, or a true nature, in contrast with the world as practically accepted. There is a certain truth in this view; for the effort to attain a predicate which does not merely repeat the subject does imply that there is an opposition. But the efforts made to return from the predicate to the subject, in a deductive movement, shows that the difference was not believed to be absolute. This is true, however, only of those fields of speculation that lie next to the highways of practical life, which lead equally in both directions, or, let us rather say, which unite while they mark separation. In the sphere of abstract ideas the sense of embarrassment was deep and constantly growing deeper. The reconstruction, accomplished on lower levels, did not attain unto those heights. Men doubted conclusions, but did not think to demand the credentials of their common presuppositions.
Side by side with the later philosophers whom we have mentioned there walked men whom we are wont to call the Sophists. They were the journalists and pamphleteers of those days, men who, without dealing profoundly with any special problem, familiarized themselves with the generalizations of workers in special fields and combined these ideas for the entertainment of the public. They were neither philosophers nor physicists, but, like some men whom we might cite from our own times, endeavored to popularize the teachings of both. Naturally they seized upon the most sweeping generalizations and the preconceptions which disclosed themselves in manifold forms. Just as naturally they had no eyes with which to detect the significance of the besetting problems at which, in matters more concrete, the masters were toiling. Hence the contradictions, revealed in the analysis we have just given of the philosophy of the age, stood out in utter nakedness.
The result was inevitable. The inability to discover a unitary predicate, more still, the failure to attain a working copula, led directly to the denial of the possibility of predication. There was no truth. Granted that it existed, it could not be known. Even if known, it could not be communicated. In these incisive words of Gorgias the conclusion of the ineffectual effort to establish a logic of science is clearly stated. But the statement is happily only the half-truth, which is almost a complete falsehood. It takes no account of the indications, everywhere present, of a needed reconstruction. Least of all does it catch the meaning of such a demand.
The Sophists did not, however, merely repeat in abstract from the teachings of the philosophers. It matters not whether they originated the movement or not; at all events they were pioneers in the field of moral philosophy. Here it was that they chiefly drew the inferences from the distinction between φύσει and νόμῳ. Nothing could have been more effective in disengaging the firmly rooted moral pre-possessions and rendering them amenable to philosophy. Just here, at last, we catch a hint of the significance of the logical process. In a striking passage in Plato's Protagoras,[106] which one is fain to regard as an essentially true reproduction of a discourse by that great man, Justice and Reverence are accorded true validity. On inquiring to what characteristic this honorable distinction is due, we find that it does not reside in themselves; it is due to the assumption that a state must exist.
Here, then, in a word, is the upshot of the logical movement. Logical predicates are essentially hypothetical, deriving their validity from the interest that moves men to affirm them. When they lose this hypothetical character, as terms within a volitional system, and set up as entities at large, they cease to function and forfeit their right to exist.