Pre-Socratics possessed a system of logic which is now for the first time brought to the notice of the modern world. Indeed, there is nothing to indicate that they had reflected on mental processes in such a way as to call for an organized body of canons regulating the forms of concepts and conclusions. Aristotle attributed the discovery of the art of dialectic to Zeno the Eleatic, and we shall see in the sequel that there was much to justify the opinion. But logic, in the technical sense, is inconceivable without concepts, and from the days of Aristotle it has been universally believed that proper definitions owe their origin to Socrates. A few crude attempts at definition, if such they may be rightly called, are referred to Empedocles and Democritus. But in so far as they were conceived in the spirit of science, they essayed to define things materially by giving, so to speak, the chemical formula for their production. Significant as this very fact is, it shows that even the rudiments of the canons of thought were not the subjects of reflection.
In his Organon Aristotle makes it evident that the demand for a regulative art of scientific discourse was created by the eristic logic-chopping of those who were most deeply influenced by the Eleatic philosophy. Indeed, the case is quite parallel to the rise of the art of rhetoric. Aristotle regarded Empedocles as the originator of that art, as he referred the beginnings of dialectic to Zeno. But the formulation of both arts in well-rounded systems came much later. As men conducted lawsuits before the days of Tisias and Corax, so also were the essential principles of logic operative and effective in practice before Aristotle gave them their abstract formulation.
While it is true, therefore, that the Pre-Socratics had no formal logic, it is equally true, and far more significant, that they either received from their predecessors or themselves developed the conceptions and the presuppositions on which the Aristotelian logic is founded. One of the objects of this study is to institute a search for some of these basic conceptions of Greek thought, almost all of which existed before the days of Socrates, and to consider their origin as well as their logical significance. The other aim here kept in view is to trace the course of thought in which the logical principles, latent in all attempts to construct and verify theories, came into play.
It is impossible, no doubt, to discover a body of thought which does not ground itself upon presuppositions. They are the warp into which the woof of the system, itself too often consisting of frayed ends of other fabrics, is woven with the delight of a supposed creator. Rarely is the thinker so conscious of his own mental processes that he is aware of what he takes for granted. Ordinarily this retirement to an interior line takes place only when one has been driven back from the advanced position which could no longer be maintained. Emerson has somewhere said: "The foregoing generations beheld God and Nature face to face; we through their eyes. Why should not we also enjoy an original relation to the universe? Why should not we have a poetry and philosophy of insight and not of tradition, and a religion by revelation to us and not the history of theirs?" The difficulty lies precisely in our faith in immediate insight and revelation, which are themselves only short-cuts of induction, psychological short circuits, conducted by media we have disregarded. Only a fundamentally critical philosophy pushes its doubt to the limit of demanding the credentials of those conceptions which have come to be regarded as axiomatic.
The need of going back of Aristotle in our quest for the truth is well shown by his attitude toward the first principles of the several sciences. To him they are immediately given—ἄμεσοι προτάσεις—and hence are ultimate a priori. The historical significance of this fact is already apparent. It means that in his day these first principles, which sum up the outcome of previous inductive movements of thought, were regarded as so conclusively established that the steps by which they had been inferred were allowed to lapse from memory.
No account of the history of thought can hope to satisfy the demands of reason that does not explain the origin of the convictions thus embodied in principles. The only acceptable explanation would be in terms of will and interest. To give such an account would, however, require the knowledge of secular pursuits and ambitions no longer obtainable. It might be fruitful of results if we could discover even the theoretical interests of the age before Thales; but we know that in modern times the direction of interest characteristic of the purely practical pursuits manifests its reformative influences in speculation a century or more after it has begun to shape the course of common life. Hence we might misinterpret the historical data if they were obtainable. But general considerations, which we need not now rehearse, as well as indications contained in the later history of thought, hereinafter sketched, point to the primacy of the practical as yielding the direction of interest that determines the course it shall take.
It was said above that the principles of science are the result of an inductive movement, and that the inductive movement is directed by an interest. Hence the principles are contained in, or rather are the express definition of, the interest that gave them birth. In other words, there is implied in all induction a process of deduction. Every stream of thought embraces not only the main current, but also an eddy, which here and there re-enters it. And this is one way of explaining the phenomenon which has long engaged the thought of philosophers, namely, the fact of successful anticipations of the discoveries of science or, more generally still, the possibility of synthetic judgments a priori. The solution of the problem is ultimately contained in its statement.88
To arrive at a stage of mentality not based on assumptions one would have, no doubt, to go back to its beginnings. Greek thought, even in the time of Thales, was well furnished with them. We cannot pause to catalogue them, but it may further our project if we consider a few of the more important. The precondition of thought as of life is that nature be uniform, or ultimately that the world be rational. This is not even, as it becomes later, a conscious demand; it is the primary ethical postulate which expresses itself in the confidence that it is so. Viewed from a certain angle it may be called the principle of sufficient reason. Closely associated with it is the universal belief of the early philosophers of Greece that everything that comes into being is bound up inseparably with that which has been before; more precisely, that there is no absolute, but only relative, Becoming. Corollaries of this axiom soon appeared in the postulates of the conservation of matter or mass, and the conservation of energy, or more properly for the ancients, of motion. Logically these principles appear to signify that the subject, while under definition, shall remain just what it is; and that, in the system constituted of subject, predicate, and copula, the terms shall "stay put" while the adjustment of verification is in progress. It is a matter of course that the constants in the great problem should become permanent landmarks.
Other corollaries derive from this same principle of uniformity. Seeing that all that comes to be in some sense already is, there appears the postulate of the unity of the world; and this unity manifests itself not only in the integrity and homogeneity of the world-ground, but also in the more ideal conception of a universal law to which all special modes of procedure in nature are ancillary. In these we recognize the insistent demand for the organization of predicate and copula. Side by side with these formulæ stands the other, which requires an ordered process of becoming and a graduated scale of existences, such as can mediate between the extremes of polarity. Such series meet us on every hand in early Greek thought. The process of rarefaction and condensation in Anaximenes, the ὁδὸς ἄνω κάτω of Heraclitus, the regular succession of the four Empedoclean elements in almost all later systems—these and other examples spontaneously occur to the mind. The significance of this conception, as the representative of an effective copula, will presently be seen. More subtle, perhaps, than any of these principles, though not allowed to go so long unchallenged, is the assumption of a φύσις, that is, the assumption that all nature is instinct with life. The logical interpretation of this postulate would seem to be that the concrete system of things—subject, predicate, copula—constitutes a totality complete in itself and needing no jog from without.
In this survey of the preconceptions of the early Greek philosophers I have employed the terms of the judgment without apology. The justification for this course must come ultimately, as for any assumption, from the success of its application to the facts. But if "logic" merely formulates in a schematic way that which in life is the manipulation
