As the Platonic doctrine of ideas came to life again in the realism, as it was called, of scholastic philosophy, so the conflicting view of his old opponent Aristotle was revived under the form of conceptualism. According to this theory the genera and species of the objective world correspond to real and permanent distinctions in the nature of things; but, apart from the conceptions by which they are represented in the intellect of God and man, those distinctions have no separate existence. Aristotle's philosophy was first brought into Europe by the Mohammedan conquerors of Spain, which became an important centre of learning in the earlier Middle Ages. Not a few Christian scholars went there to {4} study. Latin translations were made from Arabic versions of Aristotle, and in this way his doctrines became more widely known to the lecture-rooms of the Catholic world. But their derivation from infidel sources roused a prejudice against them, still further heightened by the circumstance that an Arabian commentator, Averroes, had interpreted the theology of the _Metaphysics_ in a pantheistic sense. And on any sincere reading Aristotle denied the soul's immortality which Plato had upheld. Accordingly, all through the twelfth century Platonism still dominated religious thought, and even so late as the early thirteenth century the study of Aristotle was still condemned by the Church. Nevertheless a great revolution was already in progress. As a result of the capture of Constantinople by the Crusaders in A.D. 1204 the Greek manuscripts of Aristotle's writings were brought to Paris, and at a subsequent period they were translated into Latin under the direction of St. Thomas Aquinas, the ablest of the schoolmen, who so manipulated the Peripatetic philosophy as to convert it from a battering-ram into a buttress of Catholic theology--a position still officially assigned to it at the present day. Aristotelianism, however, did not reign without a rival even in the later Middle Ages. Aquinas was a Dominican; and the jealousy of the competing Franciscan Order found expression in maintaining a certain tradition of Platonism, represented in different ways by Roger Bacon (1214-1294) and by Duns Scotus (1265-1308). In this connection we have to note the extraordinary fertility of the British islands in eminent thinkers during the Middle Ages. Besides the two last mentioned there is Eriugena ("born in Ireland"), John of Salisbury {5} (1115-1180), the first Humanist, William of Ockham, and Wycliffe, the first reformer--making six in all, a larger contribution than any other region of Europe, or indeed all the rest of Europe put together, has made to the stars of Scholasticism. This advantage is probably not due to any inherent genius for philosophy in the inhabitants of these islands, but to their relative immunity from war and to the political liberty that cannot but have been favourable to independent thought. Five out of the six were more or less inclined to