03-02-2013, 12:04 PM
Keith's white bishop is on e3.
Since pieces cannot move to a different-coloured square, they cannot capture a piece on a different coloured square (except in the case of en-passant captures - that's a complication, but it doesn't actually affect the outcome). So there are basically two wars being fought in parallel - one between the white-square pieces and one between the black-square pieces. Neither war can continue beyond the point where all the pieces of the appropriate colour on one side have been captured - the other side must have at least one piece of that colour remaining.
In the puzzle, all black's black-square pieces have been captured. But white's king and two remaining pawns (which are all black-square pieces) cannot have moved, and therefore cannot be responsible for the capture of any of black's pieces. The only piece that can have captured black's last black-square piece is the white bishop, so it has to be on a black square - therefore it is on e3, not on e4.
Since pieces cannot move to a different-coloured square, they cannot capture a piece on a different coloured square (except in the case of en-passant captures - that's a complication, but it doesn't actually affect the outcome). So there are basically two wars being fought in parallel - one between the white-square pieces and one between the black-square pieces. Neither war can continue beyond the point where all the pieces of the appropriate colour on one side have been captured - the other side must have at least one piece of that colour remaining.
In the puzzle, all black's black-square pieces have been captured. But white's king and two remaining pawns (which are all black-square pieces) cannot have moved, and therefore cannot be responsible for the capture of any of black's pieces. The only piece that can have captured black's last black-square piece is the white bishop, so it has to be on a black square - therefore it is on e3, not on e4.