Originally posted by SwissGambit
[b]If there are no proofs that e.p.p is possible, it is not possible.
Says who? On what authority?
There are no probabilities here. Either it is possible, or it is not possible. There is nothing in between, like 50% possible.
On the contrary, there are probabilities, because we don't know what White's last move was. Once the board is ...[text shortened]... board is oriented incorrectly; then you will have the right to ask for proof of en passant.[/b]
This discussion is hypothetical only. So there is not a conflict here. If either of us is right and the other is wrong doesn't really change anything. So this discussion is about amusement and amusement only.
Let's compare with a problem where a castling is involved. Here we have clear rules: If, with a retro-analysis, it shows that a castling is impossible, then castling cannot be a part of the solution.
Does this imply that e.p. must be the last move if it can be the last move, or does this imply that e.p. can't be the last move if there is another possibility of move?
About the probability: Is it really 50%-50% cabce that one or another of the two possibilites has occurred? Why not 30%-70% or any other combination? A pawn move with e.p. possibility is quite a rare occurrens, therefore an e.p. move has very low statistically frequency. So statistically the probability of an e.p. move in this position is quite low. Or not, we don't have any means to know if it were the one or the other event happened in the move before.
But I know this: The stipulation of the problem is "mate in zero moves", therefore it is mate already. Alas: No e.p. move.
The problem is a joke problem. There is no intention that it should be taken seriously. If the solution is to turn the board 180 degrees or let the player go from one side of the board to the other make it quite funny. So I settle with this. No proofs of any kind is really necessary.
And I find this thread rather amusing.