Parmenides embodied his philosophy in an epic poem, of which we have still important fragments. It is divided into two parts. In the first he discusses the conception of being. Rising far above the yet unmediated view of Xenophanes, he attains a conception of pure single being, which he sets up as absolutely opposed to every thing manifold and changeable, _i. e._, to that which has no being, and which consequently cannot be thought. From this conception of being he not only excludes all becoming and departing, but also all relation to space and time, all divisibility and movement. This being he explains as something which has not become and which does not depart, as complete and of its own kind, as unalterable and without limit, as indivisible and present though not in time, and since all these are only negative, he ascribes to it, also, as a positive determination—thought. Being and thought are therefore identical with Parmenides. This pure thought, directed to the pure being, he declares is the only true and undeceptive knowledge, in opposition to the deceptive notions concerning the manifoldness and mutability of the phenomenal. He has no hesitancy in holding that to be only a name which mortals regard as truth, viz., becoming and departing, being and not-being, change of place and vicissitude of circumstance. We must therefore be careful not to hold “the One” of Parmenides, as the collective unity of all concrete being. So much for the first part of Parmenides’ poem. After the principle that there is only being has been developed according to its negative and positive determinations, we might believe that the system was at an end. But there follows a second part, which is occupied solely with the hypothetical attempt to explain the phenomenal world and give it a physical derivation. Though firmly convinced that, according to reason and conception, there is only “the One,” yet is Parmenides unable to withdraw himself from the recognition of an appearing manifoldness and change. Forced, therefore, by his sensuous perception to enter upon a discussion of the phenomenal world, he prefaces this second part of his poem with the remark, that he had now closed what he had to say respecting the truth, and was hereafter to deal only with the opinion of a mortal. Unfortunately, this second part has been very imperfectly transmitted to us. Enough however remains to show, that he explained the phenomena of nature from the mingling of two unchangeable elements, which Aristotle, though apparently only by way of example, indicates as warm and cold, fire and earth. Concerning these two elements, Aristotle remarks still farther that Parmenides united the warmth with being, and the other element with not-being.