Topsy-turveydom has played a prodigious part in the progress of thought. The history of philosophy and science is merely a tale of development by topsy-turveydom, every new thinker simply contradicting his predecessor. Thales said water was the primitive principle of all things; so Anaximander said it was air, whereupon Anaximenes said it was matter. This made Pythagoras maintain it was not concrete matter but abstract number; whereupon Xenophanes would have it that it was not number but pure monistic being, and his disciple Zeno invented some delightful and immortal paradoxes to prove that time and motion and number and change have no existence, and only existence exists. Up comes Heraclitus, proving that existence doesn't exist, and there is nothing in the world but becoming: that so far from change not existing, nothing exists but change. It was now about time to return to earth, and so Empedocles and Democritus came along with their Atoms; thereby provoking Anaxagoras into bringing in Soul to explain things. Things were going on thus satisfactorily when the Sophists appeared on the scene to say that we didn't really know anything, because all our knowledge was subjective, so Socrates insisted that it didn't matter, because conduct was three-fourths of life. Plato retorted that it did matter, and he invented an archetypal universe of which this was a faint and distorted copy. Naturally Aristotle must contradict him by founding empirical science, which concerns itself only with this world. On his heels came the Stoics, who would have nothing to do with science except in so far as it made men virtuous, and who wanted to live soberly and severely. This provoked the neo-Platonists into craving for ecstatic union with the supernatural. The transition period from ancient philosophy to modern was one long fight between Nominalists and Realises, the one school teaching the exact opposite of the other.