Hello ! I’m a beginner at Go and I’m a little bit confused with this position.
White stones seem dead because the group doesn’t have two eyes and wherever White plays (A4 or B1), Black is able to capture the group.
However, if White decides to play elsewhere, how does Black capture the group in practice ? If Black plays in A4, White captures by playing B1 and creates a 4 living shape… If Black plays in B1, White captures by playing A4 and creates a 4 living shape in “L”… Could someone explain me ? Thank you !
The key point to understanding is that Black can capture at their leisure, there is nothing local White can do in the mean-time. Therefor Black can simply leave it to the end of the game and kill after removing all ko threats. There are rare exceptions that involve “unremovable ko-threats”. @yebellz might be along later to provide example or explanation but I don’t think I have ever seen such a thing occur in one of my games.
Note: Under Japanese rules it is just counted as dead except for scenarios I’ve never seen first-hand and under Chinese rules (area scoring) the kill can be completed without altering the score if it is necessary to demonstrate to the opponent.
From @Atorrante response I understand that the status of the 4-shape in “L” in the corner is actually not clear because Black can take the Ko and start a Ko fight…
So if White makes a threat elswhere that Black needs to answer, then White takes the Ko back, and Black needs to make an other threat elsewhere to force White to respond etc…
Am I correct ?
This particular situation you depicted happens to be quite complicated - if you are just interested in whether groups can live without two eyes, there are simpler positions which show that the answer is “yes!”.
For instance this white group is alive.
kind of? the trick is that black can basically eliminate all of white’s ko threats elsewhere before initiating the ko, thus effectively killing it
Of course in japanese rules this could cost points to eliminate those threats, so Japanese rules has a specific way of marking this dead without doing that
But as mentioned elsewhere, there are living groups with less than two eyes through “seki”, or “mutual life”, which is basically the concept you listed in the OP: neither side can profitably move to kill the other, the example just happened to be wrong for complex reasons
Depending on the definition of eyes, this group is living with 2 fake eyes.