One day a piece of paper fell from my hand. I stooped to pick it up but it was not there. There was no place it could have gone: This was just the bare corner of a room, the uncarpeted floor abutting the walls. But the page had vanished. Several plausible, I suppose I should say probable, alternative explanations coursed through my mind; for example, "It has slipped into a hidden crevice." But I was really baffled. I let it go. What else could I do? As unusual an experience as that was, it represents... read more