For two and a half centuries a small confession by Gotthold Ephraim Lessing has sat quietly at the edge of Western thought. He looked across the gap between the accidents of history and the necessities of reason, and admitted he could not leap it, however earnestly he tried. He called it a broad, ugly ditch, and he asked for help crossing it. No one came.

This book takes the ditch seriously and then does something Lessing did not dare. It refuses the two easy answers our age keeps offering—that the far bank is solid and knowable, or that nothing is real and everything is permitted. It relativizes neither the world nor the ditch, but only our hold on them. The world may be anything at all; what is admittedly a drawing is the map we carry of it.

Beginning with Lessing's ditch and with a forgotten book by Hans Vaihinger on the little words "as if," it asks how a person can stand inside a frame with the full weight of the sacred while never once forgetting that it is a frame. On the chessboard the knight must move as it moves; off the board it is a piece of carved wood. Both are true, and the whole art of an honest life lies in holding them at once—playing the game as though the board were the world, and remembering, without flinching, that it is a board.

It carries this double poise into the hardest rooms: time, causation, memory, guilt, love, the self, the universe, and the death of the people we cannot bear to lose. It is not the coldness of the skeptic, who has stopped playing, nor the blindness of the believer, who has forgotten the wood. It is a third and more difficult composure, and a strangely consoling one. A calm book about how to cross an uncrossable ditch by building, in full view of everyone including yourself, a bridge you know you drew.