From, A History of Greek Philosophy, vol. I, The early Presocratics and the Pythagoreans, Cambridge University Press, 1962, pp. 1-25.
Guthrie, Introduction to a History of Greek Philosophy
With the Greeks we stand at the beginning of rational thought in Europe. It follows that we shall not only be concerned with reasoned explanation or scientific observation, but shall be watching the emergence of these activities from the mists of a pre-scientific age. This emergence is not sudden, but slow and gradual. I shall try indeed to justify the traditional claim of Thales to be regarded as the first European philosopher; but I shall not intend by that to assert that at one bound the line was crossed between pre-rational, mythical or anthropomorphic conceptions and a purely rational and scientific outlook. No such clearly-marked line existed, or exists today. Besides appreciating what is of permanent value in Greek thought, we may also learn from observing how much latent mythology it continued to shelter within what appear to be a roof and walls of solid reason. This is naturally more obvious in the earliest period, but even Aristotle, to whom in spite of his critics in all ages we owe so much of the indispensable groundwork of abstract concepts on which our thinking is based, has some fixed ideas which we encounter with a sense of shock; for example, a conviction that the heavenly bodies are living creatures, a belief in the special perfection of circularity or sphericity, and some curious notions about the primacy of the number three which clearly antedate the beginnings of philosophical thought.
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