felt not only a need for distinct rules of conduct, but he found more or less clearly that in his own inner being there worked a force which controlled his action and allowed him to decide between good and bad, to aim for the good and avoid the bad. This force revealed itself as a highly mysterious power. Granted that it controlled the actions of many men, that its decisions between good and bad were given without the least delay and asserted themselves with all decision, if anyone asked what was the actual nature of this force, and on what foundation it built its judgments, it was then seen that both this force as well as the judgments, which appeared so natural and self-evident, were phenomena which were harder to understand than any other phenomena in the world.
So we see then that since the Persian Wars, Ethics, or the investigation of the mysterious regulator of human action—the moral law—comes to the front in Greek philosophy. Up to this time Greek philosophy had been more or less natural philosophy. It made it its duty to investigate and explain the laws which hold in the world of nature. Now nature lost interest with the philosophers even more and more. Man, or the ethical nature of humanity, became the central point of their investigations. Natural philosophy ceased to make further progress, the natural sciences were divided from philosophy; all progress of the ancient philosophy came now from the study of the spiritual nature of man and his morality.
The Sophists had already begun to despise the knowledge of nature. Socrates went still further, being of opinion that he could learn nothing from the trees, but much from the human beings in the town. Plato looked on natural philosophy as play. With that, however, the method of philosophy changed. Natural philosophy is necessarily bound to rely on the observation of nature. On the other hand, how is the moral nature of man to be observed with more certainty than through the observation of our own personality? The senses can deceive us; other men can deceive us; but we ourselves do not lie to ourselves
