If you don't have a sente move, resign

This is a go proverb from Tampere, Finland. Although it is listed here as an "almost proverb", it actually can be shown to be valid:

First, let's try to define a sente move.

Sente is a move the opponent must answer.

Yeah? Or then what? The rules allow passing, so no move can ever be sente. (Yes, this is nitpicking. That's the point of this whole exercise :-)

Sente is a move the opponent must answer locally, or he will lose a lot there.

This is still flawed, since the opponent can play somewhere else, if it gains even more. So, by this definition an "almost sente" move would be considered sente. No good.

Sente is a move, whose local answer is the best move for the opponent.

Yes, much better. Still, the opponent may choose to secure his win by playing elsewhere to remove bad aji, if he has a sufficient lead to do so. So...

Sente is a move, to which the opponent must answer locally, otherwise he will lose the game.

Almost there, but still not good enough. Namely, now you will have to define "local". Let's skip that, see e.g. this problem if you think the answer to a sente move cannot be very, very non-local.

Sente is a move, that the opponent must somehow answer, otherwise he will lose the game.

Now, if you accept this definition of "sente", then if you don't have any sente moves, this would mean that your opponent can pass after any move you make, and still win. So you should resign.

--Bass, original idea by Henri Hansen

(Sprinkle the text with these smileys here, if necessary: :-) :-) :-) :-). Thank you.)

Klaus:I always thought, that I should resign any 9 stone handicap as white without playing the first move!

HolIgor: Before I ever played my first game I thought that anybody should resign if I gave them 9 stones.

I know this is supposed to be humour and stuff but... I've had taken relevant courses at the university i'm at. (Though can't say that i'm any good at it, though i do know some) And i must say that the way you go from one proposition to another couldn't have broken more rules even if it tried. Adding arbitarly stuff to your original proposition to make it mean what you want it to mean will certainly not lead you to a logically correct proof.

well, the thing is probably that this one was indeed not a logical chain of deduction, but rather the writer tried to improve on the correspondence of his theory on what a sente is. --sigs

"must answer." to "must answer locally, or he will lose a lot there.", what do you back this up with?...

"The rules allow passing, so no move can ever be sente." You here assume (biggest cause of QED's gone wrong) that passing is part of the possible answars the opponent can make. He can make it, but then it is outside the scope of that proposition. (And if we assume that passing is something done when there are no more moves worth points to be made, then passing here would be against that)

Ellbur: I disagree that a sente move is a move that the opponent must answer or lose the game. Consider common sente yose moves. Many are sente, yet opponent may play another sente move if an unanswered follow-up to the new move is greater than the value of the gote response to the first sente move. In this case, the first player must respond to the sente move of the second player, and then the second player makes the first move to complete the unfunnished suji of the first sente move, with the second player playing the last stone. This is the key: the last stone is gote. The opponent of the last stone is sente. Sente is not absolute; a sente move has a measurable degree of sente that is equal to the value of the gote move that the opponent must use to answer it. If the opponent has a greater gote move or a sente move of greater sente, then they may play that. It is not necessary that the move must be answered or the game is lost, nor is it sufficient. If the suji is more than two moves, the last move is always gote.

DrStraw I prefer the definition that sente is a move that Black answers in a handicap game. It is at least as good as any of those here.

KfLenz That proverb seems to be equivalent to "don't play your sente moves", since if you do, you end up with a position you need to resign. Doesn't make much sense to me.

Blake I think the "proverb" (it's from Finland, according to the text above, so I don't think it can be considered as valid as a traditional one) is trying to say that, if the tempo of the game is completely against you--and there is no way for you to take the initiative--you should resign, because you're probably losing. Not exactly the same as the almost-proverb, but it makes more sense.

Bass Thanks for your comments, everybody. The "proverb" in itself is not supposed to make any sense at all, it just happened to materialize, when we were trying to define "sente" at a club meeting some time ago, and could not find a better definition than the one given above. It is of course completely stupid, but in my humble opinion it nicely illustrates the futility of trying to rigidly define an abstract concept. And no, it has nothing whatsoever to do with actual gameplay, not even here in Finland :-)

Andre Engels: I think the proverb is meant to say something like "If getting two moves in a row is not enough to win, then resign."

davos: What if you killed all your opponent's groups and he does not adhere to this proverb, should you?

lox2eagle?: According to the last sente-definition this «proverb» just states to resign if you can't do anything to win. This definition of sente in an absolute way makes no sense, and it's author doesn't state the contrary. What's the hassle?

Tamsin: I find this almost-proverb highly dubious. If sente means a move that should be answered to avoid a local loss, then what happens when the opponent has got nothing left to lose? In that case, you cannot possibly have sente against them, and yet you will be leading. Conversely, if you have a wonderful position, then you may need to defend it in gote in order to keep it. I was on the wrong end of this only a few weeks ago: at the beginning of the endgame I reckoned I was 20 points behind, but decided to do my best to catch up. Even though I got every double sente and sente point on the board, I lost by 10 points. Therefore, perhaps the almost-proverb should be "If you have nothing but sente moves, resign". LOL!

aokun: I think the discussion illustrates an important thing about sente. It may be possible to define sente rigidly but the definition is not meaningful because a rigid definition requires the person applying it to have a complete understanding of the value of alternative moves. The whole point of go is that it takes place in an environment of uncertainty. Certainly the game ends if both players have a complete understanding of the board situation. (Perhaps another almost proverb: If both players understand the board situation completely, one of them can resign with a clear conscience.) Long ago, game theory showed that a chance-free, finite game of perfect information has an equilibrium in pure strategies whose value is one of the ending game positions. Translating quickly, any game without dice, cards or hidden pieces, such as chess, go, checkers, shogi or the like, has a value. Chess is either a white win game, a black win game, or a drawn game. The problem is it is impractical to calculate which, and so we can play it on the premise that while both players lack a complete understanding, one's understanding may be better than another's. It is fun to think of go as a vast, mostly unmapped swamp, through which you dare an enemy to join you for a trek on the gamble that you can find your way out again better than he can.

The problem with the proposed definitions, including the last, for sente moves, is that there no way it is humanly possible to tell whether any move is sente except for a few life and death or reducing moves in the endgame. Sente has to be a contingent, incomplete concept or it is not a very useful one, something like this:

"A sente move is one which, if not answered with a compliant response of low value on the current board, gives its maker a follow-up move more valuable than others available to either player on the current board." This takes care of a lot of things, including the concept of chilling, i.e. how a 2-point threat can make a move sente in the endgame while a 3-3 invasion might not be sente in the opening. The contingency comes from the fact that low value and high value are hard to estimate until the very end of the game.

None of which answers very much the proposed proverb. I think it is just wrong. I'd go for: "Sente is irrelevent if you have a big enough gote move."

Not to nitpick (though that is the whole point), but having no sente moves by that definition can also mean I win no matter what my opponent responds. ~srn347