one-sided rationalistic idealism. This is recognised by clear-sighted opponents. And Schopenhauer's calling the non-rational or anti-rational element in the world 'will' helps to make plainer the real problem of evil. There is truth in the Hegelian paradox that 'pessimism is an excellent basis for optimism.' An optimist like Plotinus saw that, even if good comes of evil, the case of the optimist must fail unless evil can be shown to be a necessary constituent of the world. The Platonic and Neo-Platonic 'matter,' a principle of diremption or individuation, like time and space for Schopenhauer, was an attempt to solve this problem; but something more positive seemed to be needed as the source of the stronger manifestations of evil. To the strength of these Plato drew attention in a passage (_Republic_, x. 610[5]) where it is acknowledged that injustice confers a character of vitality and sleeplessness upon its possessor. In the notion of a blind and vehement striving, Schopenhauer supplies something adequate; only, to maintain a rational optimism, it must be regarded as a necessary element in a mixture, not as the spring of the whole. [5] Cited in one of the introductory essays to Jowett and Campbell's edition, vol. ii. Much might be said on the teleology by which he tries to educe intelligence from the primordial strife. Against his view, that it is evolved as a mere instrument for preserving races in a struggle, another may be set that is ready to hand in a dialogue of Plutarch.[6] The struggle among animals, it is there incidentally argued, has for its end to sharpen their intelligence. Both these theories are on the surface compatible with evolution. If, leaving aside the problem of mechanism, we try to verify them by the test of results, the latter undoubtedly seems the more plausible. For if the struggle was a means to the improvement of intelligence, nature has succeeded more and more; whereas, if her intention was to preserve races, she has continually failed. This argument is at any rate perfectly valid against Schopenhauer himself; for he holds in common with the optimistic teleologists that 'nature does nothing in vain.' [6] _De Sollertia Animalium_, 27.