Convinced that happiness was both necessary and attainable, but convinced also that the systems which had hitherto offered it as their reward were logically untenable, he wished to place morality on the broad basis of what was held in common by all schools, and this seemed to be the rule of obedience to Nature’s dictates,—a rule which had also the great merit of bidding men do in the name of philosophy what they already felt inclined to do without any philosophy at all. We are told, indeed, that he would not commit himself to any particular system of ethics; the inference, however, is not that he ignored the necessity of a moral law, but that he wished to extricate it from a compromising alliance with untenable speculative dogmas. Nevertheless his acceptance of Nature as a real entity was a survival of metaphysics; and his morality was, so far as it went, an incipient return to the traditions of the Old Academy. VI. We have now reached a point where Greek philosophy seems to have swung back into the position which it occupied three hundred years before, towards the close of the Peloponnesian War. The ground is again divided between naturalists and humanists, the one school offering an encyclopaedic training in physical science and exact philology, the other literary, sceptical, and limiting its attention to the more immediate interests of life; but both agreeing in the supreme importance of conduct, and differing chiefly as to whether its basis should or should not be sought in a knowledge of the external world. Materialism is again in the ascendant, to this extent at least, that no other theory is contemplated by the students of physical science; while the promise of a spiritualistic creed is to be found, if at all, in the school whose scepticism throws it back on the subjective sphere, the invisible and impalpable world of mind. The attitude of philosophy towards religion has, indeed, undergone a marked change; for the Stoic naturalists count themselves among the most strenuous supporters of beliefs and practices which their Sophistic predecessors had contemned, while the humanist criticism is cautiously guarded by at least an external conformity to established usage; but the Platonic doctrine of immortality has disappeared with the dogmatic spiritualism on which it rested; and faith in superior beings tends to dissociate itself from morality, or to become identified with a simple belief in the fixity of natural law.