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Seki with eyes question 6
    Keywords: Life & Death, Question

Yet another interesting seki with eyes:

[Diagram]
Outer stones alive (2)

This is a seki too, even though White can capture the two Black stones in the corner (but does not benefit from doing so!).

-- jvt

Why would this be a seki? White plays the 2-2 point, and can then play the 1-1 point to make 2 eyes. Something must be missing here.

-- bp

Using Chinese rules:
Black: 1 point, White: 2 points.

Using Japanese rules:
Black: 0 points, White: 0 points.


[Diagram]
Outer stones alive (2)

If White plays W1, Black will throw in with B2. White can only capture the two stones with W3 and allow Black to capture two stones with B4.

Using Chinese rules:
Black: 4 points, White: 4 points.

Using Japanese rules:
Black: 2 points, White: 2 points.

Using either ruleset, White does not gain by playing at the 2-2 point.

--unkx80


Bill: Under Japanese '89 rules, if this position remains at the end of the game, Black's two stones are considered to be alive, even though White to play can capture them. The following is not real play, which has ended. Rather it is a demonstration.

[Diagram]
Gone but not dead

After the play is over, White claims that the BC stones are dead. And indeed, she can capture them with W1 - W3. However:

jvt: This is taken straight out of Life-and-Death example 2 in the Japanese Rules 1989.
The two Black stones are alive: if White captures Black's two stones, Black can play two new stones (at B2 and B4) which White cannot capture. Since there is a dame, the position is a seki.

Bill: Jean-Pierre's point, which had originally slipped my mind, is that the capture of the BC stones allows new living stones (B2 and B4) to be played. Therefore, at the end of play, the BC stones are considered to be alive.
It sounds peculiar, but the Japanese '89 rules for post-play demonstrations provide a logical basis for most of the special rulings of the Japanese '49 rules.



This is a copy of the living page "Seki with eyes question 6" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.