Parmenides once had, probably in his later years, a moment of the very purest abstraction, undimmed by any reality, perfectly lifeless; this moment--un-Greek, like no other in the two centuries of the Tragic Age--the product of which is the doctrine of "Being," became a boundary-stone for his own life, which divided it into two periods; at the same time however the same moment divides the pre-Socratic thinking into two halves, of which the first might be called the Anaximandrian, the second the Parmenidean. The first period in Parmenides' own philosophising bears still the signature of Anaximander; this period produced a detailed philosophic-physical system as answer to Anaximander's questions. When later that icy abstraction-horror caught him, and the simplest proposition treating of "Being" and "Not-Being" was advanced by him, then among the many older doctrines thrown by him upon the scrap heap was also his own system. However he does not appear to have lost all paternal piety towards the strong and well-shapen child of his youth, and he saved himself therefore by saying: "It is true there is only one right way; if one however wants at any time to betake oneself to another, then my earlier opinion according to its purity and consequence alone is right." Sheltering himself with this phrase he has allowed his former physical system a worthy and extensive space in his great poem on Nature, which really was to proclaim the new discernment as the only signpost to truth. This fatherly regard, even though an error should have crept in through it, is a remainder of human feeling, in a nature quite petrified by logical rigidity and almost changed into a thinking-machine.