Diogenes of Apollônia (probably on the Black Sea), lived in the later half of the fifth century B.C.
His longest surviving work was that On Natural Science; he also wrote, and mentioned in his main work, separate treatises on Meteorology, and On the Nature of Man; and an attack on the Natural Scientists, whom he called Sophists.
1. In starting any thesis, it seems to me, one should put forward as one's point of departure something incontrovertible; the expression should be simple and dignified.
2. It seems to me, to sum up the whole matter, that all existing things are created by the alteration of the same thing, and are the same thing. This is very obvious. For if the things now existing in this universe—earth and water and air and fire and all the other things which are seen to exist in this world: if any one of these were different in its own (essential) nature, and were not the same thing which was transformed in many ways and changed, in no way could things mix with one another, nor could there be any profit or damage which accrued from one thing to another, nor could any plant grow out of the earth, nor any animal or any other thing come into being, unless it were so compounded as to be the same. But all these things come into being in different forms at different times by changes of the same (substance), and they return to the same.
3. Such a distribution would not have been possible without Intelligence, (namely) that all things should have their measure: