Author: Russell Reagan
Date: 10:15:46 01/29/02
From the FIDE Laws of Chess:
"Article 9: Check
9.1
The king is in "check" when the square it occupies is attacked by one or more of
the opponent's pieces; in this case, the latter is/are said to be "checking" the
king. A player may not make a move which leaves his king on a square attacked by
any of his opponent's pieces.
9.2
Check must be parried by the move immediately following. If any check cannot be
parried, the king is said to be "checkmated" ("mated").
9.3
Declaring a check is not obligatory.
[Merely polite! Playing an illegal move does not imply the loss of the game: see
Article 8.1.]"
Article 9.1 states, "The king is in "check" when the square it occupies is
attacked by one or more of the opponent's pieces." This is the part I'm
particularly interested in. Let's take the following position.
[D] 8/4k3/3n4/8/1B2K3/7P/8/8 w - - 0 1
What is defined as attacking a square? In this position, the knight is sort of
attacking the king, but it can't move to any square. So if it were black's turn
to move, the knight couldn't capture the white king, so is it really attacking
the white king? I believe this does happen to be check, from my experience in
playing chess and reading about it, but I'm trying to find the justification for
it being check. From a scientific/evidence based view, the only justification I
can come up with is that this is not check.
I can find no definition of attack in the dictionary that would put the white
king in check in this position. The closest definitions that I could find were,
"To fall upon with force; to assail, as with force and arms; to assault" and "to
threaten (a piece in chess) with immediate capture" (most other definitions had
some form of human factor such as incorporating emotions). In this position, the
knight is not in any way falling upon the white king with force, assailing with
force or arms, or assaulting. The second definition which is specific to chess
also does not put the white king in check. The black knight is not threatening
immediate capture of the white king since on black's move, the knight cannot
move, and therefore cannot capture any piece, including the white king. If I
were to attack you, I would undertake offensive actions against you, probably
with the intent of harming you in some way. The black knight, in fact, can bring
no amount of harm to the white king because he himself is unable to move,
leading one to believe that the white knight is not attacking the white king,
thus the white king is not in check in this position, even though common sense
and experience tells us that the white king is in check.
If someone could point out the source of the rule that makes the white king in
check in this position and clarify what is check and what isn't, along with what
is defined as attacking a square and what isn't, I would appreciate it.
I got to thinking about all of this in the debate over whether to generate 100%
legal moves and detect pins statically or whether to let the illegal moving of
pinned pieces be handled by retracting moves that lead to positions where the
side not to move is in check. The definition of what is an attack and what is
not matters greatly here. If a pinned piece can attack, then either method of
generating legal moves is fine. If a pinned piece cannot attack, then you can't
use the method of retracting moves of pinned pieces, since you would end up
having to detect if the piece attacking the king is pinned, when you end up
doing static pin detection anyway.
Perhaps the rules need to be clarified, because there seems to be somewhat of a
contradiction. I look forward to hearing people's thoughts on this.
Russell
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