Parmenides

Parmenides of Elea was a Greek philosopher of the late sixth and early fifth centuries BCE who set out, in a poem, the first sustained philosophical argument to survive from Greece. He argued that what truly is cannot come into being, perish, change or move, and that the world of change reported by the senses is therefore a matter of mere opinion. The claim was so radical, and argued so rigorously, that much of later Greek philosophy can be read as an attempt to answer it.

Parmenides came from Elea, a small Greek city on the west coast of southern Italy, later called Velia by the Romans. It had been founded around 540 BCE by refugees from Phocaea in Ionia, who fled when the Persians of the Achaemenid Empire conquered their homeland. Diogenes Laertius reports that he came from a wealthy and distinguished family, and later writers, including Plutarch and the geographer Strabo, say he drew up laws for Elea that its citizens swore to uphold every year.

His dates are uncertain. Ancient chronographers placed his prime around 500 BCE, but these schemes were often artificial, linking a philosopher's maturity to famous events or to the birth of a supposed pupil. Plato, in his dialogue Parmenides, describes him visiting Athens at about sixty-five with his pupil Zeno and conversing with a very young Socrates, which would place his birth around 515 BCE. Whether that meeting really happened is doubted, but many scholars accept the approximate chronology it implies. When and how he died is not recorded. Ancient sources connect him with the poet-philosopher Xenophanes, who spent time in the Greek west, and with a Pythagorean named Ameinias, but these teacher and pupil links may be later reconstructions.

Parmenides wrote a single work in hexameter verse, the metre of Homer and Hesiod, later given the title On Nature. About 160 lines survive, mostly preserved by the sixth-century CE Neoplatonist Simplicius, who quoted long passages because he knew the book had become rare, and by the sceptic Sextus Empiricus, who preserved the opening. Thanks to Simplicius, the central argument appears to survive almost complete, but much of the second half of the poem is lost.

The poem opens with a journey. The narrator, a young man, rides in a chariot guided by the daughters of the Sun through the gates of the paths of Night and Day, where an unnamed goddess welcomes him. She promises to teach him two things: the unshaken heart of well-rounded truth, and the opinions of mortals, in which there is no true reliability. The rest of the poem is her speech.

The goddess explains that there are only two conceivable paths of inquiry: that something is and cannot not be, and that it is not and must not be. The second, she says, cannot be followed at all, because what is not can neither be known nor spoken of. She also condemns a third path taken by ordinary mortals, who wander as if two-headed, treating being and not-being as both the same and not the same. People who trust their eyes and ears, and believe things come into existence and pass away, are following this confused path.

From these premises she draws striking conclusions. What is cannot have come into being, since it could only have come from what is not, which is impossible; for the same reason it cannot perish. It is whole and undivided, since there is nothing other than it to separate one part from another. It does not move or change, and it is complete and lacks nothing, like the bulk of a well-rounded sphere. Knowledge, on this view, must be guided by reason rather than by the senses.

What Parmenides meant by "what is" is one of the most debated questions in ancient philosophy. The traditional reading, going back to Plato and Aristotle, holds that he was a strict monist, claiming that only one thing exists and that plurality and change are illusions. Other interpreters argue that he was setting out the conditions any genuine object of knowledge must meet, or that his "is" concerns what a thing fundamentally is, not simply whether it exists. Whatever the right reading, he was the first Greek thinker to make the logical analysis of being a subject of argument in its own right.

The second part of the poem gives an account of the physical world as mortals understand it, built on two opposed principles, light or fire and dark night. The goddess presents it as deceptive, yet offers it in detail, covering the stars, the sun and moon, the origin of humans and animals, and embryology. Later reports credit Parmenides with several astronomical observations, including that the moon shines with light borrowed from the sun, and possibly that the morning and evening stars are the same body, the planet Venus. Why he included a cosmology he had declared unreliable is unclear. He may have wanted to offer the best possible version of the mistaken view, or he may have thought it had a limited value of its own.

Parmenides' argument set the agenda for his successors. His pupil Zeno of Elea devised his famous paradoxes of motion, including Achilles and the tortoise, to defend him by showing that belief in plurality and motion leads to absurdities, and Melissus of Samos restated the Eleatic position in prose. Philosophers of nature who came after him, including Empedocles, Anaxagoras and the atomists Leucippus and Democritus, accepted that nothing comes from nothing but tried to explain change as the mixing and separating of unchanging elements or particles.

Plato took Parmenides with great seriousness. His distinction between unchanging Forms known by reason and the changing world of the senses owes much to the Eleatic contrast between truth and opinion, and in the Sophist he describes his own attempt to make sense of not-being as a kind of attack on "father Parmenides". Aristotle developed his theory of potentiality and actuality partly to escape the Parmenidean dilemma. For modern readers Parmenides remains a founder of metaphysics and logic, and a central figure in ancient Greek philosophy, even though many of his conclusions have struck almost everyone since as impossible to accept.