VII. So far as I know, no historian of Greek philosophy has clearly laid it down that the word which was used by the early cosmologists to express this idea of a permanent and primary substance was none other than φύσις; and that the title Περὶ φύσεως, so commonly given to philosophical works of the sixth and fifth centuries B.C.,[15] means simply _Concerning the Primary Substance_. Both Plato and Aristotle use the term in this sense when they are discussing the earlier philosophy,[16] and its history shows clearly enough what its original meaning must have been. In Greek philosophical language, φύσις always means that which is primary, fundamental, and persistent, as opposed to what is secondary, derivative, and transient; what is “given,” as opposed to that which is made or becomes. It is what is there to begin with. It is true that Plato and his successors also identify φύσις with the best or most normal condition of a thing; but that is just because they held the goal of any development to be prior to the process by which it is reached. Such an idea was wholly unknown to the pioneers of philosophy. They sought the explanation of the incomplete world we know, not in the end, but in the beginning. It seemed to them that, if only they could strip off all the modifications which Art and Chance had introduced, they would get at the ultimately real; and so the search after φύσις, first in the world at large and afterwards in human society, became the chief interest of the age we have to deal with. Footnote 15: I do not mean to imply that the philosophers used this title themselves; for early prose writings had no titles. The writer mentioned his name and the subject of his work in the first sentence, as Herodotos, for instance, does. Footnote 16: Plato, _Laws_, 892 c 2, φύσιν βούλονται λέγειν γένεσιν (_i.e._ τὸ ἐξ οὗ γίγνεται) τὴν περὶ τὰ πρῶτα (_i.e._ τὴν τῶν πρώτων). Arist. _Phys._ Β, 1. 193 a 21, διόπερ οἱ μὲν πῦρ, οἱ δὲ γῆν, οἱ δ’ ἀέρα φασίν, οἱ δὲ ὗδωρ, οἱ δ’ ἔνια τούτων, οἱ δὲ πάντα ταῦτα τὴν φύσιν εἶναι τὴν τῶν ὄντων.