The elaborate letters which Seneca has left us on distinctive tenets of the Stoical school, such as the equality of vices or the evil of the affections, have now little more than an historic interest; but the general tone of his writings gives them a permanent importance, for they reflect and foster a certain type of excellence which, since the extinction of Stoicism, has had no adequate expression in literature. The prevailing moral tone of Plutarch, on the other hand, being formed mainly on the prominence of the amiable virtues, has been eclipsed or transcended by the Christian writers, but his definite contributions to philosophy and morals are more important than those of Seneca. He has left us one of the best works on superstition, and one of the most ingenious works on Providence, we possess. He was probably the first writer who advocated very strongly humanity to animals on the broad ground of universal benevolence, as distinguished from the Pythagorean doctrine of transmigration, and he was also remarkable, beyond all his contemporaries, for his high sense of female excellence and of the sanctity of female love. The Romans had at all times cared more for the practical tendency of a system of philosophy than for its logical or speculative consistency. One of the chief attractions of Stoicism, in their eyes, had been that its main object was not to build a system of opinion, but to propose a pattern of life,(388) and Stoicism itself was only adapted to the Roman character after it had been simplified by Panætius.(389) Although the system could never free itself altogether from that hardness which rendered it so unsuited for an advanced civilisation, it was profoundly modified by the later Stoics, who rarely scrupled to temper it by the admixture of new doctrines. Seneca himself was by no means an unmixed Stoic. If Epictetus was more nearly so, this was probably because the extreme hardship he underwent made him dwell more than his contemporaries upon the importance of fortitude and endurance. Marcus Aurelius was surrounded by the disciples of the most various schools, and his Stoicism was much tinctured by the milder and more religious spirit of Platonism. The Stoics, like all other men, felt the moral current of the time, though they yielded to it less readily than some others. In Thrasea, who occupied in his age a position analogous to that of Cato in an earlier period, we find little or nothing of the asperity and hardness of his great prototype. In the writings of the later Stoics, if we find the same elements as in those of their predecessors, these elements are at least combined in different proportions.