Parmenides of Elea (early 5th century BCE) was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides describes two views of reality. In "the way of truth" (a part of the poem), he explains how reality (coined as "what-is") is one, change is impossible, and existence is timeless, uniform, necessary, and unchanging. In "the way of opinion," he explains the world of appearances, in which one's sensory faculties lead to conceptions which are false and deceitful. These ideas strongly influenced the whole of Western philosophy, perhaps most notably through its effect on Plato.
Parmenides was born in the Greek colony of Elea (now Ascea), which, according to Herodotus, had been founded shortly before 535 BCE. He was descended from a wealthy and illustrious family. His dates are uncertain; according to Diogenes Laërtius, he flourished just before 500 BCE, which would put his year of birth near 540 BCE, but Plato has him visiting Athens at the age of 65, when Socrates was a young man, c. 450 BCE, which, if true, suggests a year of birth of c. 515 BCE. He was said to have been a pupil of Xenophanes, and regardless of whether they actually knew each other, Xenophanes' philosophy is the most obvious influence on Parmenides. Diogenes Laërtius also describes Parmenides as a disciple of "Ameinias, son of Diochaites, the Pythagorean"; but there are no obvious Pythagorean elements in his thought. The first hero cult of a philosopher we know of was Parmenides' dedication of a heroon to his teacher Ameinias in Elea. Parmenides was the founder of the School of Elea, which also included Zeno of Elea and Melissus of Samos. Of his life in Elea, it was said that he had written the laws of the city. His most important pupil was Zeno, who according to Plato, was twenty-five years his junior, and was his eromenos. Parmenides had a large influence on Plato, who not only named a dialogue, Parmenides, after him, but always spoke of him with veneration.