The famous statement, “All I know is that I do not know,” is attributed-questionably, according to some scholars-to the ancient Greek philosopher Socrates (c. 470-399 BCE), based on two dialogues written by his disciple Plato (c. 424-c. 348 BCE).
In The Republic (c. 360 BCE), Socrates concludes a discussion with Thrasymachus on “justice” by saying, “the result of the discussion, as far as I’m concerned, is that I know nothing, for when I don’t know what justice is, I’ll hardly know whether it is a kind of virtue or not, or whether a person who has it is happy or unhappy.”
In The Apology (399 BCE), Socrates says of a well-respected politician that “he knows nothing, and thinks that he knows; I neither know nor think that I know.” The resulting slogan was adopted by later thinkers and incorporated into the tradition that became known as “Academic Skepticism.” Rather than believing that it is impossible to know anything, Academic Skeptics actually claim only that we can know very little about reality—namely, truths of logic and mathematics. This contrasts with Pyrrhonian skepticism, which involves an attitude of doubting every positive judgment, including logic and mathematics.
A serious problem with Socrates’s statements is that he seems committed to an incoherent position. If he truly does not know anything, then it is false that he knows that; but if he does know he does not know anything, then it is false that he does not know anything. Thus, the claim “I know that I do not know” is self-defeating (resulting in the statement also being known as the Socratic paradox). In response, many scholars argue that this is an uncharitable reading of Plato. They contend that Socrates’s claims are expressed in a particular context, referring only to specific concepts and not to knowledge generally (“Justice” in The Republic, and “beauty” and “goodness” in The Apology).