The human soul is of triple nature. The highest part, the rational soul (τὸ λογιστικόν), is seated in the head; the emotional soul (τὸ θυμοειδές) in the heart; the appetitive soul (τὸ ἐπιθυμητικόν) in the belly. Over these two lower souls the reasoning part should hold control, as a driver over two unruly steeds[6]. The rational soul has existed before birth, and may hope for immortality, for it is knit up with the idea of ‘being.’ Ultimately it may even attain to perfection, if it is purified as by fire from baser elements that have attached themselves to it. [Sidenote: Ethics and Politics.] =64.= Plato himself does not formulate an ethical ideal of the same precision that his successors used, but we infer from his works a goal towards which he points. Thus the ethical end for each man is the greatest possible participation in the idea of the good, the closest attainable imitation of the deity. The virtue of each part of the human soul lies in the fit performance of its proper work; that of the reasoning soul is Wisdom (σοφία); of the emotional soul Courage (ἀνδρεία); of the appetitive soul Soberness (σοφροσύνη). Over all (it is hinted rather than stated) rules the supreme virtue of Justice (δικαιοσύνη), assigning to each part its proper function. Thus the four cardinal virtues are deduced as a practical application from the Platonic psychology. The high position assigned to Justice leads up to the practical doctrine of Moderation (μετριότης); even the virtues are restricted both in their intensity and in their spheres of work, and if any virtue passes its proper limit it becomes changed into the vice that borders on it. Thus the ideal of practical life is the ‘moderate man,’ calm, considerate, and self-respecting, touched with a warm flow of feeling, but never carried away into excitement; and even this ideal is strictly subordinate to that of the life of philosophic contemplation. The ideal State is modelled on the individual man. To the three parts of the soul correspond three classes of citizens; the rulers, whose virtue is Wisdom; the guardians, on whom Courage is incumbent; the labourers and tradesmen, who owe the State Soberness and obedience. Thus the political system to which Plato leans is that of an Aristocracy; for the middle class in his state has only an executive part in the government, and the lower orders are entirely excluded from it. [Sidenote: Aristotle.] =65.= By far the greatest of Plato’s pupils was ARISTOTLE of Stagira (384-322 B.C.), who introduced into philosophy, now convulsed by the disputes of the disciples of Socrates, a spirit of reconciliation. From his point of view the various contentions are not so much erroneous as defective. To attain the truth we need first to collect the various opinions that are commonly held, and then to seek the reconciling formula of which each one is a partial statement. [Sidenote: The ten categories.]