Parmenides: the way of truth

Parmenides of Elea (early 5th century BCE) wrote a philosophical poem in epic verse. Its argument is short, strange, and relentless — and it forced every later Greek thinker, including Plato and Aristotle, to answer it. He is the founder of the Eleatic school and, arguably, of deductive metaphysics.

The goddess lays out two ways of inquiry. The Way of Truth: that it is, and that it cannot not be. The Way of Opinion (or the way of not-being): that it is not, and that it must not be. Only the first is thinkable; the second, she says, is a path that cannot be followed at all.

The engine of the whole poem is one claim (B2–B3): you cannot think or speak of “what is not.” To think is always to think of something — of what is. The moment you try to think of sheer nothing, there is no object there to think. So what-is-not cannot be grasped, cannot be said, and cannot serve as anything real.

From “what-is-not is unthinkable,” Parmenides deduces the properties of Being (B8). It is ungenerated and imperishable. For if it came to be, it must have come from what-is-not — but there is no such thing to come from, and no reason it would appear at one moment rather than another. Coming-to-be and passing-away are therefore ruled out.

The same premise makes Being one, continuous, and indivisible. To divide it you would need gaps of what-is-not between the pieces — but there is no not-being to do the separating. So there are no gaps, no parts, no plurality: reality is a single seamless whole.

And it is changeless and complete. Any change would mean Being becoming something it currently is not — reintroducing not-being through the back door. So it rests the same, in the same place, by itself (B8). Parmenides even compares it to a well-rounded sphere, equally balanced in every direction: perfect, whole, needing nothing.

This is why Parmenides elevates reason over the senses. Your eyes and ears report a world full of coming-to-be, motion, and plurality. But the goddess warns (B7) not to let habit born of much experience force you along the senses’ road; judge instead by reasoning (logos). Where argument and perception conflict, argument wins.

The poem’s third part is the Way of Opinion (doxa): the goddess herself narrates a cosmology built from two basic opposites, Light and Night. Why include a physics she has just declared untrustworthy? Probably as the best possible account of the world of appearances — offered so that no mortal opinion may outstrip you (B8) — while insisting it never rises to Truth.