“Knowing yourself is the beginning of all wisdom” — did Aristotle say it?

It is widely credited to Aristotle, but the sentence has not been found in any of his surviving works. The idea behind it is much older: “Know thyself” was inscribed at the temple of Apollo at Delphi, and Plato has Socrates discuss it in the Phaedrus and the Protagoras.

What it means

Before you can judge the world well, you need to understand yourself — your motives, your blind spots, your habits of mind. Wisdom starts with that honest look inward.

Where it comes from

The line appears on quote sites and posters credited to Aristotle, usually without a book or page. It does not appear in Aristotle's surviving works as far as we can find. Wikiquote's “Wisdom” page tags it “Nicomachean Ethics” without a book or chapter, but the sentence is not in the Ethics, and it is not among the sayings on Wikiquote's own Aristotle page.

The thought itself has a real ancient source. “Know thyself” (gnōthi seauton) was one of the maxims inscribed at Apollo's temple at Delphi. In Plato's Protagoras (343b) Socrates names it alongside “Nothing overmuch”, and in the Phaedrus (229e) he says he is not yet able, “as the Delphic inscription has it, to know myself”.

Questions

Did Aristotle say “knowing yourself is the beginning of all wisdom”?

It hasn't been found in his surviving works. The idea goes back to the Delphic maxim “Know thyself”, which predates Aristotle.

Where does “know thyself” come from?

It was inscribed at the temple of Apollo at Delphi. Plato has Socrates cite it in the Protagoras (343b) and the Phaedrus (229e).

What does the quote mean?

That understanding yourself — your motives and biases — is the first step to judging anything else wisely.