Socrates claimed he was the wisest man because he knew he knew nothing

According to Plato's Apology, the Oracle at Delphi declared Socrates the wisest man in Athens. Puzzled — he claimed no wisdom — Socrates interrogated politicians, poets, and craftsmen, and discovered each believed themselves more knowledgeable than they were. He concluded his advantage was not superior knowledge but an awareness of his own ignorance. This 'Socratic ignorance' became foundational to the Socratic method: asking questions not to share knowledge but to expose the limits of assumed certainty. The irony is that 'I know that I know nothing' is itself a claim to know something — a paradox Socrates was aware of.

Source: Plato, Apology (c. 399 BC)