A question of rulebook pedantry:
- One can claim a draw when the same position occurs the third time, the same player having the move.
- Two positions are not the same if the earlier allows a capture en passant and the later does not, though men of the same kind stand on the same squares in both positions.
So much I understand. However, what if the pawn that could otherwise have captured en passant happens to be pinned against its own king? In this case, one might say that the pawn had the right to capture en passant but could not exercise it. Alternately, one might insist that a right that cannot be exercised were in fact no right.
I suppose that it comes to how one defines the word right.
The reason this is a question of rulebook pedantry is because it might, conceivably, legally affect whether one could claim a draw if the position recurred. For the purpose of the draw rule, are two positions indeed the same if, in the earlier position, a pawn had the right to capture en passant but could not exercise it because of a pin?
To be clear: My question does not regard how fantastically unlikely such a situation would be ever to arise in actual play, nor if it has ever occurred. My question regards only what the rule would be if it did.
Your answer merits extra appreciation if you can support it with any reasonably authoritative reference!
I know no reason that anyone should be following these updates any longer -- and I rather suspect that no one is reading (if you are not reading, you are probably wise) -- but, for the permanent record and in response to a reader's reasonable request, I have deleted parts of the second and first updates. If the deletions still don't suit, further edits by interested others naturally remain welcome.
@CraigYoung characterizes the first update [as originally written] as a "diatribe." I think that he has a point. A Stackexchange question is not the right forum for the asker (me) to extemporize on the philosopy of rulebook writing. As originally written, above, the question was indeed just a question -- and was not originally meant as anything other than a request for information. What the answers seem to me to have revealed however is that no authoritative answer is possible at the present time. The answers occasioned a discussion, and the discussion seemed worth preserving, whence the first update.
I called the original question "pedantic" to poke a bit of deserved fun at myself, of course. My inner David Hilbert, as it were, wants the rules of chess to be logically complete; but the real, original David Hilbert was a wise man, a deep mathematician but also a shrewd judge of his audience. He could approach such questions with a sense of humor and a light touch, understanding that the matter of logical completeness would not fascinate everyone as much as it did him. Dr. Hilbert saved his earnestness for audiences prepared to appreciate it.
If you will let me don the cloak of earnestness for a moment: Each chess player can judge for himself how much or how little chess loses by failing logically to complete its rules, but surely chess gains nothing by this failure. Chess has a body, the FIDE, whose reasonable, permanent decisions in such matters would command broad respect, except that the FIDE seems mired in endless scandal and has never clearly rendered the decisions in question. So, if you're a Hilbert type like me, you're stuck, aren't you?
There is no rule. There could be. There should be. But there isn't. I admit that I don't like that.
@JamesTomasino's fine answer below is recommended to all interested readers. His logic looks pretty good, his angle is attractive, his judgment seems sound, and he may be right. I do not disagree with him, but I am not yet convinced.
The reason is this. There exists a school of rulebook construction with which I admittedly do not hold (and to which I do not suggest that @JamesTomasino belongs). In that school, a rule is to be enforced even if the rule's writer never considered the point to which the rule is applied. More precisely, the rule's language is to be enforced.
Actually, this might be a tolerable way to construe a rulebook, except that we have ample experience to suggest that, in cases such as this, two, different, reasonable people will infer two, different rules from the same, flawed language. Each reasonably believes that he stands upon "the rock of the law." The rules of chess however are to be a logical construct, not a linguistic one. If we are arguing over what the words mean, and if no consensus exists, then it is the words that are at fault. Such words shirk their duty.
Anderssen v. Kieseritzky may be poetic. The rulebook by which they play however is supposed to be precise. If it is not, then this is a real lack in the rulebook.
Here again is the useful reference @JamesTomasino has kindly provided to the FIDE handbook, section 9.2. After reading it thrice, I can only conclude that the rule is [hard for me to understand.] What are "the possible moves of all the pieces of both players"? Taken literally, "all the pieces" (what ever happened to the traditional phrase "all the men"? but let that pass) of one player have no moves at all, since it is his opponent's turn. Now, of course, obviously, that is not what the rule means, but what it does mean is far from clear.
To muddy the waters further, see the interesting discussion between USCF TDs @Andrew has discovered and brought to our attention.
It seems to me that the answer we are reaching here is that there exists no generally agreed-upon interpretation of the rules in these corner cases. That's too bad. I know what I think the rule should be, but what I think is irrelevant to this discussion, because I am no Staunton or Steinitz and no one cares (or should care) what I think. My chief concern is not whether this rule or that rule might be the better, but only that there in fact be a rule.
Actually, it seems to me that there is a deeper problem. The FIDE Handbook differs from the equivalent publication of the American Contract Bridge League in that the latter draws a clear distinction between the mechanics of the game and guidelines of player conduct. In the FIDE Handbook, the two are sort of all mixed up together.