Eternal life

hi guys,

I was watching this and the question came up:
why does black have to play at a?
why not play at E1 and capture the white stone?

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Black’s locally dead if they do that, but maybe I misunderstand why it’s eternal life?

Yeah, afaict White just plays on a themselves and kills Black

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why would black be dead with that?
black could make capture those 4 stones and survive by creating eyes.
I still don’t get why would black play there and not the other spot.


White getting to play a creates a bulky 5 shape, so there’s only ever 1 eye there (if Black does not play a in the given position)


If Black played at E1, then White would play at C1 to create bulky-five shape


In this position, note that A is a false eye. Black could capture the five White stones with a play at B, but that be futile and Black would still be dead, since White would answer by playing at C.

If the life and death status of this corner swings the outcome of the game, then the game should get stuck in an endless cycle (under Japanese rules and traditional Chinese rules), which results in the game being declared a “no result”.

See Eternal Life at Sensei's Library for more information.

Note: OGS implements a simplified form of the Chinese rules, where a superko rule is always applied. This removes the possibility of “no results”, and long-cycle situations would just become ko fights.


yeah I know this
but I can’t find out how can white form bulky 5.

Hi, Thanks for answering. I got it.

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Is that board on OGS? How did you get the white stones without the black outline?

It is a screenshot of an SGF editor, BesoGo

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