History of Logic

LOGIC, HISTORY OF. Logic arose, at least for the West ern world, in the golden age of Greek speculation which culmi nated in Plato and Aristotle. There is an Indian logic, it is true, but its priority is still disputed. In any case, no influence upon Greek thought can be shown. The movement which ends in the logic of Aristotle is self-contained.

Early Nature Philosophers.—Logic needs as its presuppo sitions that thought should distinguish itself from things and from sense, that the problem of validity should be seen to be raised in the field of thought itself, and that analysis of the structure of thought should be recognized as the one way of solution. Thought is somewhat late in coming to self-consciousness. Im plied in every contrast of principle and fact, of rule and appli cation, involved as we see after the event, most decisively when we react correctly upon a world incorrectly perceived, thought is yet not reflected on in the common experience. Its so-called natural logic is only the potentiality of logic. The same thing is true of the first stage of Greek philosophy. In seeking for a single material principle underlying the multiplicity of phenomena, the first nature-philosophers, Thales and the rest, did indeed raise the problem of the one and the many, the endeavour to answer which must at last lead to logic. But it is only from a point of view won by later speculation that it can be said that they sought to determine the predicates of the single subject-reality, or to establish the permanent subject of varied and varying predi cates. A further step, then, was necessary, and it was taken at any rate by the Eleatics, when they opposed their thought to the thought of others, as the way of truth in contrast to the way of opinion. It was Zeno, the controversialist of the Eleatic school who was regarded in after times as the "discoverer" of dialectic.

The Sophists.

In the history of the origins of logic, the sophistic age is simply the age of the free play of thought in which men were aware that in a sense anything can be debated and not yet aware of the sense in which all things cannot be so. It is the age of discussion used as a universal solvent, before it has been brought to book by a deliberate unfolding of the prin ciples of the structure of thought determining and limiting the movement of thought itself. The sophists furthered the transi tion from dialectic to logic in two ways. In the first place they

made it possible. Incessant questioning leads to answers. Hair splitting, even when mischievous in intent, leads to distinctions of value. Paradoxical insistence on the accidents of speech-f orms and thought-f orms leads in the end to perception of the essen tials. Secondly they made it necessary. The spirit of debate run riot evokes a counter-spirit to order and control it. The result is a self-limiting dialectic. This higher dialectic is a logic. It is no accident that the first of the philosophical sophists, Gorgias, on the one hand, is Eleatic in his affinities, and on the other raises in the characteristic formula of his intellectual nihilism issues which are as much logical and epistemological as ontological. The meaning of the copula and the relation of thoughts to the objects of which they are thoughts are as much involved as the nature of being. It is equally no accident that the name of Protagoras is to be connected, in Plato's view at least, with the rival school of Heracliteans. The problems raised by the relativism of Pro tagoras are no less fundamentally problems of the nature of knowl edge and of the structure of thought. The Theaetetus, indeed, in which Plato essays to deal with them, is in the broad sense of the word logical, the first distinctively logical treatise that has come down to us.

Socrates.

Among the pioneers of the sophistic age Socrates stands apart. He has no other instrument than the dialectic of his compeers, and he is as far off as the rest from a criticism of the instrument, but he uses it differently and with a difference of aim. He construes the give and take of the debate-game with extreme rigour. The rhetorical element must be exorcised. The set harangue of teacher to pupil, in which steps in argument are slurred and the semblance of co-enquiry is rendered nugatory, must be eliminated. The interlocutors must in truth render an account under the stimulus of organized heckling from their equals or superiors in debating ability. And the aim is heuristic, though often enough the search ends in no overt positive conclusion. Something can be found, and something is found. Common names are fitted for use by the would-be users being first delivered from abortive conceptions, and thereupon enabled to bring to the birth living and organic notions.