=60.= During this fourth century B.C. the foundations were laid of the four philosophical schools which were destined to vie one with another for the allegiance of the Roman world. The Socratic schools which we have already mentioned, those of the Cynics and Cyrenaics, did not perhaps altogether die out; in particular the Cynic missionaries appear to have been a social force until the second century B.C. But their intellectual basis was too narrow to admit of their effective transplantation to new soil. At the end of the century each gave place to a new school, which preserved the central doctrines of its predecessor. The Socratic paradoxes were handed on from the Cynics to the Stoics; the doctrine that pleasure is the good was accepted by Epicurus. Stoics and Epicureans disputed with a bitterness as yet unequalled, finding themselves just as much opposed upon the subjects of logic and physics, which they introduced anew into popular philosophy, as upon the questions of ethics on which their antipathies were inherited. Between them stood two schools which had meanwhile established themselves. Plato, himself a companion of Socrates, founded the Academy at Athens about 380 B.C.; and if he did not impress his own teaching upon it with absolute fixity, still the school flourished under a succession of leaders, always proud of the fame of its founder, and rendering him at least a nominal allegiance. From the Academy branched off the school of the Peripatetics, founded by Plato’s pupil Aristotle about 350 B.C. After Aristotle’s death this school gravitated towards the Academics, and in later centuries there seemed little difference, if any, between the two. If Stoicism may be called the child of Cynism, it largely drew nourishment from these two schools and their founders. Some account of the teaching of Plato and Aristotle is therefore needed here, partly because of the great importance of both in the general history of philosophy, partly because of their direct influence upon the subject of this book. On account of the much greater prominence of the Academy in the later history we shall often use this term to refer to the general teaching of the two allied schools. [Sidenote: Plato.]