The earliest attempts of the Greek philosophers to present philosophy in a complete and articulated order—attempts generally attributed to the Stoics, the schoolmen of antiquity—made it a tripartite whole. These three parts were Logic, Physics, and Ethics. In their entirety they were meant to form a cycle of unified knowledge, satisfying the needs of theory as well as practice. As time went on, however, the situation changed: and if the old names remained, their scope and value suffered many changes. New interests and curiosities, due to altered circumstances, brought other departments of reality under the focus of investigation besides those which had been primarily discussed under the old names. Inquiries became more specialised, and each tended to segregate itself from the rest as an independent field of science. The result was that in modern times the territory still marked by the ancient titles had shrunk to a mere phantom of its former bulk. Almost indeed things had come to such a pass that the time-honoured figures had sunk into the misery of _rois fainéants_; while the real business of knowledge was discharged by the younger and less conventional lines of research which the needs and fashions of the time had called up. Thus Logic, in the narrow formal sense, was turned into an “art” of argumentation and a system of technical rules for the analysis and synthesis of academical discussion. Physics or Natural Philosophy restricted itself to the elaboration of some metaphysical postulates or hypotheses regarding the general modes of physical operation. And Ethics came to be a very unpractical discussion of subtleties regarding moral faculty and moral standard. Meanwhile a theory of scientific method and of the laws governing the growth of intelligence and formation of ideas grew up, and left the older logic to perish of formality and inanition. The successive departments of physical science, each in turn asserting its independence, finally left Natural Philosophy no alternative between clinging to its outworn hypotheses and abstract generalities, or identifying itself (as Newton in his great book put it) with the _Principia Mathematica_ of the physical sciences. Ethics, in its turn, saw itself, on one hand, replaced by psychological inquiries into the relations between the feelings and the will and the intelligence; while, on the other hand, a host of social, historical, economical, and other researches cut it off from the real facts of human life, and left it no more than the endless debates on the logical and metaphysical issues involved in free-will and conscience, duty and merit.