Socrates is the Greek philosopher traditionally associated with the saying “I know that I know nothing.”
The phrase is a later paraphrase of ideas presented in Plato's Apology, rather than a sentence that appears in exactly that form in Plato's surviving Greek text. In the dialogue, Socrates explains that he is wiser than others because he does not pretend to know what he does not know.
This attitude became central to the Socratic method. Socrates questioned politicians, poets, and craftsmen about justice, virtue, courage, and wisdom, often exposing contradictions in their confident answers. His goal was not simply to win arguments, but to encourage intellectual humility and clearer reasoning.
The quotation is also connected with the Oracle of Delphi, which reportedly declared Socrates the wisest man in Athens. Socrates interpreted the oracle by investigating people who claimed expertise and concluding that recognizing one's ignorance was a form of wisdom. Plato and Aristotle were major philosophers influenced by Socrates, but neither is the canonical answer to this quotation.