tile

The Toynbee tiles litter the Earth, but are unknown to most. Trivia buffs are almost certain to know of them. You're deciding right now whether to look that up. If you can't resist, you're smarter than most. But now, if you do look it up, you'll never know whether you looked it up because you would have looked it up anyway, or because you wanted to feel smart. Unless you would have looked it up anyway, because you know who you are. Or do you?