With the idea of subsumption and subordination to law, we pass at once to the Stoic ethics. For Zeno, the end of life was self-consistency; for Cleanthes, consistency with Nature; for Chrysippus, both the one and the other.[42] The still surviving individualism of the Cynics is represented in the first of these principles; the religious inspiration of the Stoa in the second; and the comprehensiveness of its great systematising intellect in the last. On the other hand, there is a vagueness about the idea of self-consistency which seems to date from a time when Stoicism was less a new and exclusive school than an endeavour to appropriate whatever was best in the older schools. For to be consistent is the common ideal of all philosophy, and is just what distinguishes it from the uncalculating impulsiveness of ordinary life, the chance inspirations of ordinary thought. But the Peripatetic who chose knowledge as his highest good differed widely from the Hedonist who made pleasure or painlessness his end; and even if they agreed in thinking that the highest pleasure is yielded by knowledge, the Stoic himself would assert that the object of their common pursuit was with both alike essentially unmoral. He would, no doubt, maintain that the self-consistency of any theory but his own was a delusion, and that all false moralities would, if consistently acted out, inevitably land their professors in a contradiction.[43] Yet the absence of contradiction, although a valuable verification, is too negative a mark to serve for the sole test of rightness; and thus we are led on to the more specific standard of conformability to Nature, whether our own or that of the universe as a whole. Here again a difficulty presents itself. The idea of Nature had taken such a powerful hold on the Greek mind that it was employed by every school in turn—except perhaps by the extreme sceptics, still faithful to the traditions of Protagoras and Gorgias—and was confidently appealed to in support of the most divergent ethical systems. We find it occupying a prominent place both in Plato’s _Laws_ and in Aristotle’s _Politics_; while the maxim, Follow Nature, was borrowed by Zeno himself from Polemo, the head of the Academy, or perhaps from Polemo’s predecessor, Xenocrates. And Epicurus, the great opponent of Stoicism, maintained, not without plausibility, that every animal is led by Nature to pursue its own pleasure in preference to any other end.[44] Thus, when Cleanthes declared that pleasure was unnatural,[45] he and the Epicureans could not have been talking about the same thing. They must have meant something different by pleasure or by nature or by both.