Page:Early Greek philosophy by John Burnet, 3rd edition, 1920.djvu/88

74 advance. In fact, it makes the Milesian cosmology consistent for the first time; since a theory which explains everything as a form of a single substance is clearly bound to regard all differences as quantitative. The only way to save the unity of the primary substance is to say that all diversities are due to the presence of more or less of it in a given space. And when once this step has been taken, it is no longer necessary to make the primary substance something "distinct from the elements," to use Aristotle's inaccurate but convenient phrase; it may just as well be one of them.

27. The air Anaximenes speaks of includes a good deal that we should not call by the name. In its normal condition, when most evenly distributed, it is invisible, and it then corresponds to our "air"; it is the breath we inhale and the wind that blows. That is why he called it πνεῦμα. On the other hand, the old idea that mist or vapour is condensed air, is still accepted without question. It was Empedokles, we shall see, who first discovered that what we call air was a distinct corporeal substance, and not identical either with vapour or with empty space. In the earlier cosmologists "air" is always a form of vapour, and even darkness is a form of "air." It was Empedokles who cleared up this point too by showing that darkness is a shadow.