8
7
6
5
4
3
2
1
	a	b	c	d	e	f	g	h

Pretty ingenious, eh?

Now try one of Raymond Smullyan's Masterpieces.

Raymond Smullyan

WHITE TO MATE IN ONE MOVE  © Raymond Smullyan

1. It's White's move, so the Black King is not in check.
Conclusion: The Black King does not stand on d8.

2. This means that either the Black King stands on c8 or
the White King is in check from the Black Rook.
If the latter, the Black King must have just moved from c8 to d7.
Conclusion: The Black King stands on one of two squares - c8 or d7.

3. If the White Pawn on c7 now captures the Black Rook and is
promoted to a Knight, the Black King will be mated regardless
of whether he stands on c8 or d7.   Think about it.