That which is, is ...it cannot be more or less. There is... as much of — Parmenides

"The Greek tradition was a complete contrast to that of the Far East. ...the Greeks placed logic at the pinnacle of human thinking. Their sceptical attitude towards the wielding of non-being as some sort of something that could be subject to logical development was exemplified by Parmenides influential arguments against the concept of empty space. ...He maintained that you can only speak about what is: what is not cannot be thought of, and what cannot be thought of cannot be. ...more unexpected was the further conclusion that time, motion nor change could exist either."

"The crisis at the heart of Parmenides argument, "is or is not," rules out any candidate for an ultimate entity in an explanation of what there is that is subject to coming-to-be, passing-away, or alteration of any sort. Such an entity must be a whole, complete, unchanging unity: it must be a thing that is of a single kind … But it does not follow from this that there can be only one such entity. Parmenides arguments allow for a plurality of fundamental, predicationally unified entities that can be used to explain the world reported by the senses."

"What is clear is that Parmenides is making a conscious attempt at some kind of a new start. Like Descartes, he is trying to find an unassailable starting-point on which something further can be built. This search is understandable, given the intellectual situation of the time. The principles of the Milesians had yielded no one clearly true system, but a number of rival ones — in itself a scandal. Heraclitus had made the whole of cosmology suspect by revealing deep-seated contradictions at its heart. In the background, the Pythagoreans were directly or indirectly stimulating new lines of thought and using them, perhaps, for their own mysterious purposes."

"Of the philosophers, Thales is vaguely reported to have taught that souls are immortal. But neither he nor his immediate successors... believed in the immortality of particular souls... This doctrine belongs to the Orphic tradition. In Heracleitus and Parmenides we find the two doctrines of immortality... implicit in mysticism, separated... for the first time. Heracleitus is the champion of the Dionysiac... life and death... in an unending cycle; Parmenides, under Orphic influence, teaches... Soul has fallen from... light and reality to the dark and unreal... bodily existence. This, however, is... only the way of opinion... [Parmenides] feels.... that... substantiality... is not so easily got rid of. But he will not give up... eternal substance. The most interesting fragment of Parmenides... seems to enunciate, for the first time in Greek thought, the mystical doctrine of eternity as a timeless Now, as opposed to the popular... unending succession. There remains then only to give an account of one way—that real Being exists. Many signs... showing... it is unborn, indestructible, entire, unique, unshakable, and unending. It never was, and it never will be, since it is all together present in the Now, one and indivisible. Empedocles... repudiates... Parmenides, probably on the ground that he reduces the world of time and change to nullity... thus leaves no pathway from appearance to reality. His doctrine of the soul’s exile and wanderings is... Orphic doctrine, which Pindar also gives... in the second Olympian Ode. The Soul sins by separating itself from God... from love and a choice of strife ’ in the place of harmony. The immortal Soul is... love and strife blended; the body... only an alien garment... perishes at death. ...Empedocles describes the Soul as a ratio, or harmony ...the complex of...strife... bound... by the principle of unity...love...Parmenides ...may be ...rejects the Pytdhagorean doctrines ...finds truth in static materialism."

"What-is was not generated from what-is-not, because what-is-not cannot give rise to anything in addition to itself. This is the first enunciation of the principle "out of nothing, nothing comes to be,"? which was implicit in earlier Greek thought even as far back as Hesiod and which afterwards, because of Parmenides, became a touchstone for subsequent Greek cosmogonies. These arguments show that coming to be from what-is-not is impossible, which is... relevant in the first stage of a cosmogony. The arguments say nothing of more familiar cases of coming to be, which can be described in terms of changes among already existing things."

"Greek philosophy returned for some time to the concept of the One in the teachings of Parmenides... His most important contribution... was, perhaps, that he introduced a purely logical argument into metaphysics. "One cannot know what is not—that is impossible—nor utter it; for it is the same thing that can be thought and that can be." Therefore, only the One is, and there is no becoming or passing away. Parmenides denied the existence of empty space for logical reasons. Since all change requires empty space... he dismissed change as an illusion."