Yesterday, upon the stair,You go to the city centre, or to the shopping complex, and you see hundreds of anonymous strangers passing by. You assume they are normal, flesh-and-blood people going about their normal, flesh-and-blood activities, just like you. Indeed, it would be a very strange world if it were not so. But it is a very strange world. So how do you know that every last one of those anonymous strangers is really, physically present?
I met a man who wasn't there.
Antigonish, by Hughes Mearns (1899)