Empedokles regarded the “roots of all things” as eternal. Nothing can come from nothing or pass away into nothing (fr. 12); what is _is_, and there is no room for coming into being and passing away (fr. 8). Further, Aristotle tells us, he taught that they were unchangeable.[584] This Empedokles expressed by saying that “they are what they are” (frs. 17, 34; 21, 13), and are “always alike.” Again, they are all “equal,” a statement which seemed strange to Aristotle,[585] but was quite intelligible in the days of Empedokles. Above all, the elements are ultimate. All other bodies, as Aristotle puts it, might be divided till you came to the elements; but Empedokles could give no further account of these without saying (as he did not) that there is an element of which Fire and the rest are in turn composed.[586] Footnote 584: Arist. _de Gen. Corr._ Β, 1. 329 b 1. Footnote 585: _Ibid._ Β, 6. 333 a 16. Footnote 586: _Ibid._ Α, 8. 325 b 19 (R. P. 164 e). This was so completely misunderstood by later writers that they actually attribute to Empedokles the doctrine of στοιχεῖα πρὸ τῶν στοιχείων (Aet. 1. 13, 1; 17, 3). The criticism of the Pythagoreans and Plato had made the hypothesis of elements almost unintelligible to Aristotle, and _a fortiori_ to his successors. As Plato put it (_Tim._ 48 b 8), they were “not even syllables,” let alone “letters” (στοιχεῖα). That is why Aristotle, who derived them from something more primary, calls them τὰ καλούμενα στοιχεῖα (Diels, _Elementum_, p. 25). The “four roots” are given as an exhaustive enumeration of the elements (fr. 23 _sub fin._); for they account for all the qualities presented by the world to the senses. When we find, as we do, that the school of medicine which regarded Empedokles as its founder identified the four elements with the “opposites,” the hot and the cold, the moist and the dry, which formed the theoretical foundation of its system, we see at once how the theory is related to previous views of reality.[587] To put it shortly, what Empedokles did was to take the opposites of Anaximander and to declare that they were “things,” each of which was real in the Parmenidean sense. We must remember that the conception of quality had not yet been formed. Anaximander had no doubt regarded his “opposites” as things; though, before the time of Parmenides, no one had fully realised how much was implied in saying that anything is a thing. That is the stage we have now reached. There is still no conception of quality, but there is a clear apprehension of what is involved in saying that a thing _is_. Footnote 587: We know from Menon that Philistion put the matter in this way. See p. 235, _n._ 527.