White Mates in 8

No, do not adjust your monitor.

White to play and mate in 12.

Originally posted by THUDandBLUNDER
No, do not adjust your monitor.

[fen]RnBqkBnR/PPppppPP/8/8/8/8/ppPPPPpp/rNbQKbNr w - - [/fen]

It's a pity the position is illegal.

Originally posted by BigDoggProblem
It's a pity the position is illegal.

Yes, but it's only a puzzle.

Originally posted by BigDoggProblem
It's a pity the position is illegal.

How is it illegal? Neither King is in check and no Pawns are on their eighth ranks...what rule is it breaking?

Originally posted by AThousandYoung
How is it illegal? Neither King is in check and no Pawns are on their eighth ranks...what rule is it breaking?

And no pieces or pawns have been captured.
So how did the pawns pass each other?

Originally posted by THUDandBLUNDER
And no pieces or pawns have been captured.
So how did the pawns pass each other?

There is a difference (maybe just symantics?) in illegal and possible.
ATY said the position is not illegal, you are saying it is just not possible.

The question I have then, is: Is the position illegal, or just impossible (or both?)

Originally posted by Alcra
There is a difference (maybe just symantics?) in illegal and possible.
ATY said the position is not illegal, you are saying it is just not possible.

The question I have then, is: Is the position illegal, or just impossible (or both?)

I would say that a position is illegal if it cannot be arrived at by a series of legal moves.

I say impossible but legal.

Originally posted by AThousandYoung
I say impossible but legal.

Somewhat predicably, USCF gives a less-than-useful definition:
Illegal position - A position in which both Kings are in check or a number of factors are involved which make a position illegal.
http://www.uschess.org/beginners/glossary.php

But the definition is clear in the world of chess problems (which is what I posted).
Legal position (n.): a position that can be reached from the initial array by a game consisting entirely of legal moves, however bizarre. Conventionally, any chess problem should have a legal position. Naturally then, an illegal position is a position that cannot be reached by a legal game. (Oxford Companion to Chess).

See also Article 8 of FIDE Laws.
http://www.chessvariants.com/fidelaws.html

Edit: THUDandBLUNDER beat me to it!

Originally posted by THUDandBLUNDER
Somewhat predicably, USCF gives a less-than-useful definition:
Illegal position - A position in which both Kings are in check or a number of factors are involved which make a position illegal.
http://www.uschess.org/beginners/glossary.php

But the definition is clear in the world of chess problems (which is what I posted).
Legal position (n.): a ...[text shortened]... n to Chess).

See also Article 8 of FIDE Laws.
http://www.chessvariants.com/fidelaws.html

All right then. I bow down to your superior researching efforts. It's illegal! Give yourself a ticket, THUDandBLUNDER!!

Originally posted by AThousandYoung
All right then. I bow down to your superior researching efforts. It's illegal! Give yourself a ticket, THUDandBLUNDER!!

I don't think the definition matters too much.

Originally posted by THUDandBLUNDER
I don't think the definition matters too much.

It does matter. As your source pointed out, most compositions begin from legal positions. Can you really claim you have given checkmate if the position was not legal to start with? In a game, the opponent may able to have the game replayed from the last legal position. An excellent defense against 'forced' mate!

If legality is deliberately shirked, it makes the problem 'unorthodox' and more like a 'fairy' problem (even though I hate that term).

Originally posted by BigDoggProblem
It does matter. As your source pointed out, most compositions begin from legal positions. Can you really claim you have given checkmate if the position was not legal to start with? In a game, the opponent may able to have the game replayed from the last legal position. An excellent defense against 'forced' mate!

If legality is deliberately shirke ...[text shortened]... kes the problem 'unorthodox' and more like a 'fairy' problem (even though I hate that term).

IMO, it matters for games.
Less so for problems unless they are retros.
In fact, I think I will post a few of my favourites.