See It, Know It

Potter Stewart was the US Supreme Court justice who said, in the case Jacobellis v. Ohio (1964), “I shall not today attempt further to define (pornography)… But I know it when I see it…”

I was reading In Praise of Slowness by Carl HonorĂ©, and he quotes Augustine: “What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not…” (Book XI, ~400AD)

So Mr. Stewart had a bit of prior art on that idea.