It seems well nigh impossible that a man of Nicolas' age and training should have reasoned so clearly, but the fact remains that he did, and that all of modern philosophy is built upon the foundations he laid. Since his time a great many other theories of knowledge have been put forward, but all have worked, in a sort of circle, back to Nicolas. It would be interesting, perhaps, to trace the course and history of these variations and denials, but such an enterprise is beyond the scope of the present inquiry. Nicolas by no means gave the world a complete and wholly credible system of philosophy. Until the day of his death scholasticism was dominant in the world that he knew, and it retained its old hold upon human thought, in fact, for nearly two hundred years thereafter. Not until Descartes, in 1619, made his famous resolution "to take nothing for the truth without clear knowledge that it is such," did humanity in general begin to realize, as Huxley says, that there was sanctity in doubt. And even Descartes could not shake himself free of the supernaturalism and other balderdash which yet colored philosophy. He laid down, for all time, the emancipating doctrine that "the profession of belief in propositions, of the truth of which there is no sufficient evidence, is immoral"--a doctrine that might well be called the Magna Charta of human thought[3]--but it should not be forgotten that he also laid down other doctrines and that many of them were visionary and silly. The philosophers after him rid their minds of the old ideas but slowly and there were frequent reversions to the ancient delusion that a man's mind is a function of his soul--whatever that may be--and not of his body. It was common, indeed, for a philosopher to set out with sane, debatable, conceivable ideas--and then to go soaring into the idealistic clouds.[4] Only in our own time have men come to understand that the ego, for all its seeming independence, is nothing more than the sum of inherited race experience--that a man's soul, his conscience and his attitude of mind are things he has inherited from his ancestors, just as he has inherited his two eyes, his ten toes and his firm belief in signs, portents and immortality. Only in our own time have men ceased seeking a golden key to all riddles, and sat themselves down to solve one riddle at a time.