Little is known of Parmenides’ (pahr-MEHN-eh-deez) life except that he created some of the laws of his native Elea and perhaps visited Athens in 450 b.c.e. Diogenes Laertius states that he was a Pythagorean in his youth and a pupil of Xenophanes. Scholars note, however, that there are no significant Pythagorean elements in Parmenides’ philosophy, and they question his relationship to Xenophanes. He wrote a poem under the traditional title, Peri physeōs (fifth century b.c.e.; The Fragments of Parmenides, 1869, commonly known as On Nature), one-third of which is extant. In the conventional form of epic hexameter, Parmenides promulgates his new philosophical ideas, which led to the foundation of the Eleatic School.
In On Nature, Parmenides introduces the theme of philosophical instruction: A young charioteer, the philosopher himself, embarks on a journey in the domain of the goddess of truth, justice, and retribution in order to learn the nature of true existence. Following Xenophanes’ monotheistic understanding of the universe, Parmenides proclaims that true reality is solely “an object of thought and speech,” and if “that which exists, cannot not-exist,” then “there is not that which does not exist.” This theoretical premise is announced by the just goddess, who teaches the young philosopher about the two ways of learning. One is the way toward true knowledge, that reality is “unoriginated, imperishable, whole, indivisible, steadfast and complete”; the other is the way toward false opinion, based on sense perceptions, that reality is originated, perishable, multiple, divisible, and in constant change over time and space.