“I know it when I see it”

“I KNOW IT WHEN I SEE IT,” phrase that usually describes something that is hard to define but may be recognized by intuition. It became famous when United States Supreme Court Justice Potter Stewart concurred with his opinion in the case of Jacobellis v. Ohio (1964). Justice Stewart used the expression to give a vague standard for pornography concerning the Louis Malle film, Les Amants. He wrote: “I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description [‘hard-core pornography’], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.”