Parmenides
Parmenides of Elea ( /pɑrˈmɛnɨdiːz əv ˈɛliə/; Ancient Greek: Παρμενίδης ὁ Ἐλεάτης; fl. 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.
Read more about Parmenides: Life, On Nature, Interpretations of Parmenides, Influence On The Development of Science