Parmenides

Greek philosopher, born in Elea, Magna Grecia, toward the end of the VI century B.C. - died during the mid half of the V century. B.C.). Not much is known about him. His fellow citizens called on him to draft the laws of his city Elea, where he also founded a school, the Eleatic School.

The only known work of Parmenides is a poem titled On Nature. In the poem Parmenides elaborates the concept of Being. He argues that changes in the physical world are illusory, and, contrary to common sense, states that the reality of Being is unchanging, unique, motionless, eternal. Being is opposed to Becoming, identified with reality and can only be know through reason, not the senses.

Parmenides thought is guided by a rigorous determination of thetruth (aletheia), the philosophical discourse and its contents, in contrast to the opinion (doxa), of common thought. According to him, the tool that allows us to seek and define truth is reasoning, a logical process that is expressed in an exact language. Opinion, on the other hand, is derived through the senses, and give rise to a contradictory and meaningless knowledge. This is the antithesis of reason and experience which many will try to resolve throughout the course of centuries.

Thought and being are the same.
Whatever can be spoken or thought of necessarily is, since it is possible for it to be, but it is not possible for nothing to be.