Parmenides

Parmenides of Elea (born c. 515 BCE) founded the Eleatic school in the Greek
colony of Elea in southern Italy and ranks among the most rigorous of the
Presocratic philosophers. His single known work, a philosophical poem
composed in epic hexameters, is preserved in substantial fragments. In its
proem the narrator is carried in a chariot to the dwelling of a goddess, who
promises to reveal both "the unshaken heart of well-rounded truth" and the
deceptive opinions of mortals.

The argument of the Way of Truth is austere and uncompromising. Parmenides
begins from what he takes to be a self-evident premise: that which is, is,
and that which is not, is not. From this he reasons that "what is not" cannot
be thought or spoken, since to think is always to think of something. Genuine
being, therefore, can neither come to be nor pass away, for that would require
a passage from not-being to being. Being must be ungenerated, imperishable,
whole, unchanging, and complete.

These conclusions place Parmenides in direct opposition to the world of
ordinary experience. The senses present us with a manifold of things that
move, change, and perish; but reason, Parmenides insists, reveals these
appearances to be illusory. Plurality and motion are impossible, for they
would require the void — empty space, a kind of "what is not" — and the void
cannot exist. Reality is one, continuous, and motionless, however
stubbornly the senses report otherwise.

The second part of the poem, the Way of Opinion, presents a cosmology of the
familiar changing world, but the goddess explicitly marks it as the deceptive
belief of mortals, offered so that no rival account might surpass the
listener's understanding. Why Parmenides included this account at all remains
a celebrated puzzle of ancient scholarship.

Parmenides' challenge — that thought and being are bound together, and that
change may be a rational impossibility — set the agenda for much that
followed. His pupil Zeno devised paradoxes to defend the master's monism,
and the pluralist philosophers who came after, including the atomists,
constructed their systems precisely to answer his demand that nothing comes
from nothing. To engage with Parmenides is to confront the deepest tension
between reason and the evidence of the senses.