This being the sum and substance of the teaching of Thales, we may naturally ask why, on account of such a crude and undeveloped idea, he should be given the title of the father of philosophy. Why should philosophy be said to begin here in particular? Now, the significance of Thales is not that his water-philosophy has any value in itself, but that this was the first recorded attempt to explain the universe on naturalistic and scientific principles, without the aid of myths and anthropomorphic gods. Moreover, Thales propounded the problem, and determined the direction and character, of all pre-Socratic philosophy. The fundamental thought of that period was, that under the multiplicity of the world there must be a single ultimate principle. The problem of all philosophers from Thales to Anaxagoras was, what is the nature of that first principle from which all things have issued? Their systems are all attempts to answer this question, and may be classified according to their different replies. Thus Thales asserted that the ultimate reality is water, Anaximander indefinite matter, Anaximenes air, the Pythagoreans number, the Eleatics Being, Heracleitus fire, Empedocles the four elements, Democritus atoms, and so on. The first period is thus {23} essentially cosmological in character, and it was Thales who determined the character. His importance is that he was the first to propound the question, not that he gave any rational reply to it. We saw in the first chapter, that man is naturally a materialist, and that philosophy is the movement from sensuous to non-sensuous thought. As we should expect, then, philosophy begins in materialism. The first answer to the question, what the ultimate reality is, places the nature of that reality in a sensuous object, water. The other members of the Ionic school, Anaximander, and Anaximenes, are also materialists. And from their time onwards we can trace the gradual rise of thought, with occasional breaks and relapses, from this sensualism of the Ionics, through the semi-sensuous idealism of the Eleatics, to the highest point of pure non-sensuous thought, the idealism of Plato and Aristotle. It is important to keep in mind, then, that the history of philosophy is not a mere chaotic hotch-potch of opinions and theories, succeeding each other without connection or order. It is a logical and historical evolution, each step in which is determined by the last, and advances beyond the last towards a definite goal. The goal, of course, is visible to us, but was not visible to the early thinkers themselves.