How do you look for something when you don't know what it is?

You walk into the kitchen and can't remember what you came for. You stand there, and then you know it when you see it: the scissors. Somehow you were looking for the scissors without knowing you were. The question is how any search for the genuinely unknown can work at all. Plato's Meno sets the trap. You can't look for what you already know, Meno argues, and you can't look for what you don't know, because you wouldn't recognize it if you found it. Socrates' answer is startling: learning is remembering. He questions an untaught slave boy about a geometry problem until the boy works his way to the answer, as if he had known it all along. Later in the dialogue Socrates draws the distinction this question is named for. Someone with a correct belief about the road to Larissa, who has never traveled it, can guide you there as well as someone who has. But true beliefs, he says, are like Daedalus's legendary walking statues, liable to wander off; working out why a belief is true is what anchors it and makes it knowledge. Augustine worried at the same puzzle in his Confessions. When you lose something and find it again, you recognize it, so some trace of it must have stayed with you all along. Science found a looser answer in luck. The novelist Horace Walpole coined the word serendipity in 1754 for the knack of finding valuable things you weren't looking for. In 1928 Alexander Fleming came back from holiday to find that mold had killed the bacteria around it on a dish he had left out. He was studying staphylococci, not hunting for a drug, but years of searching for natural germ-killers had taught him to recognize one when he saw it. Think of something important you found without knowing you were looking for it. How did you recognize it when it came?

Meno: And how will you inquire, Socrates, into that which you do not know? What will you put forth as the subject of inquiry? And if you find what you want, how will you ever know that this is the thing which you did not know? Socrates: I know, Meno, what you mean… You argue that a man cannot inquire either about that which he knows, or about that which he does not know; for if he knows, he has no need to inquire; and if not, he cannot.