Parmenides

Parmenides (c. 515–450 BCE) was a Pre-Socratic philosopher of Elea in southern Italy and the founding figure of the Eleatic school. He set out his philosophy in a hexameter poem, On Nature, framed as a revelation delivered to him by a goddess, of which substantial fragments survive.

The poem divides into the Way of Truth and the Way of Opinion, and its rigorous argument made Parmenides the first thinker to reason systematically from premises about being itself, profoundly shaping the course of Greek metaphysics.

For the mind-power lineage, Parmenides argues that what truly is—Being—is one, ungenerated, indestructible, indivisible, and changeless; that “what is, is, and what is not, is not”; and that coming-to-be and passing-away, plurality and motion, belong only to the deceptive Way of Opinion, the world of appearances.

Most striking is his claim that “thinking and being are the same”—that thought and that which is are inseparable, since one can only think of what is. This identification of thought with reality, and the demotion of the changing sensible world to mere appearance against an unchanging unity grasped by reason, makes Parmenides a foundational ancestor of idealism: the conviction that ultimate reality is one, mental in character, and known by mind rather than the senses.