You can’t
But t4 kills the white group
1 Like
Note that the play by black leading up to this event is normally called “stalling” - playing dead stones into the opponent’s territory. White was entitled to pass at the point that two eyes were formed and the outside liberties removed. If it continued after that, then report black for stalling.
“You can’t kill a group with two eyes unless the owner lets you”.
BUT if both players agree that it can be killed, that means the owner can’t see how to save it, which means it is dead.
“A group is only alive if the owner can see how to save it” 
That’s why I said “normally called stalling”. In this instance, your opponent was presenting you with a real threat, so they were not in fact stalling (and this is why moderators judging these reports have a hard job: it’s never black and white).
It’s an instructive game for white: it shows that you need to be prepared to sacrifice a stone to keep a group alive.
“Don’t go fishing when your house is on fire”
1 Like
Yeah, good advice, though in this case the player was not so much fishing, as “following”.
The best move might not be in the vicinity of the opponent’s last stone 
1 Like
the relevant sequence went as shown below. White continued playing their own threat to cut when a local response was needed after the threat at 2
2 Likes
True - I was focussed on the fact that the local response was not very local 
If black was stalling then so was white in the middle. But in reality neither were, they were just beginners doing beginner things and moderators should keep their noses out and let beginners be beginners. White lived in the middle where white should have died if black was more skilled, and white died on the right where white should have lived if white was more skilled.
9 Likes
That’s why there’s the concept of Pass-alive at Sensei's Library.
Related: Does the following group have two eyes?
6 Likes
Ouch… Yeah, gotta be very careful with end-game, weird things can happen when the liberties run out ^^
3 Likes
That’s why I used the word “normally” ( to contrast with this specific situation) and added
The “these reports” that I referred to are the stream of “stalling” reports that the community files.
Maybe we should update the moderation templates in this style.
“Sorry, we are not investigating your report of stalling, because the community prefers that moderators keep their noses out of beginner games”.
3 Likes
More generally, killing a group with two “eyes” is possible if one of the “eyes” is a big eye in which you can form an eye with at least 2 spaces.
2 Likes
I’d say that group has no eyes (though it’s obviously alive by virtue of being able to easily make 2 eyes if needed), so I think “eye” means something like “a set of points enclosed by stones of one color such that the other color cannot live inside”
1 Like
In the position from the OP, I’d say White has 0 eyes, not 2. It appears from the discussion that White used to have 2 eyes in the lower-right, but in the screenshot posted, I don’t see any eyes for White, but rather a capturing race that White has lost
3 Likes
How spicy was it??
4 Likes
Lol not at all, I just got the user’s colours mixed up and commented as though the winner had posted not the loser.
4 Likes
Yeah. I (white) lost the game on this group being lost. I just never realized this was possible as when you learn you get told a group with two eyes can’t be captured. As I have never seen this kind of thing before I didn’t keep track of liberties until it was too late. I should have killed the black group in the corner a move or two earlier.
One more Lesson learned.
I agree this was two beginners fumbling about. I have only just started playing go again after a 25 year break. I probably never got above 25k 25 years ago as I had not played enough games. I played about 2-3 across the board games a week for 2 years or so but not every week so suspect I’d only played about 100 games in total.
So I feel like a beginner. Certainly was not happy with this game. I allowed Black too much influence in the center, my stones were too thick and lots of other bad stuff I am sure.
Hugh
3 Likes
Have your teacher, or anyone else told you the “reason” for “2 eyes”? It’s not part of the rule, but a combination of the rules allows a group with certain properties to be kept without being captured if opts for a pass.
The 3 rules involved are
- one side can only play one move in a turn
- The capture rule checks the liberties of the opponent’s group first, and removes them, before checking the liberties of your own group (hence a group with just one single intersection left connection to it, even if it is within the group, can still be captured)
- a player can opt to pass instead of playing a stone on the board
If any of these 3 rules are changed, then the property allowing a group to stay on the board will change. Like the new game combined cards and Go I posted, allow more than one stone to be played on the board according to the cards drawn, meaning, more than one stone can be placed in one turn, hence you will need to be careful to check if your opponent actually got a card that has the exact shape of stones fit into your eye space.
And for some Atari Go (especially first capture wins), the pass move is not an option, so if no players ever capture a stone, when both sides have one group and 2 single-space eyes left, the one who plays next will be forced to fill one od the eye, and allow the opponent to capture the whole group (thus preventing draw).
(And changing the capturing rule, obviously will change what kinds of groups can stay alive on the board). If you understand the reason why these properties allow a group to stay alive, then you will also understand why seki is just another form of this property without the need to “define” any group “alive or dead” (or even define what is an “eye”).
1 Like
‘A group with 2 eyes can’t be killed’ was stated in a book I read many years ago. It was explained that it was not a rule but a consequence on the no suicide or self capture rule.
This is the first time I have seen this situation.
‘a group is captured when it’s last liberty is taken’ shows that it is possible to kill a group with 2 eyes if a parasite group is inside one of the eyes with at least two liberties.
I don’t think I am the only one, there is a Redit thread on the same ‘descovery’ by a beginner.
The rule specifically forbids suicide is not related to the property of groups with 2 eyes (it affects when a group has the last liberty in a ko situation where it can be used as a ko threat). There are rules like Ing’s rules, or New Zealand rules that allow suicide, and it doesn’t change the property I mentioned above (nor the situation of seki). The difference is that whether the "suicide into a space that didn’t fill the opponent’s last liberty, counts as a move or not. (those with forbid suicide, count it as 0 move, and those allow suicide count it as 1 move, and both don’t affect the said group with at least 2 liberties left)
In the most strict sense in the primitive form, only a single intersection size’s free space surrounded by the same colored stones can be called “an eye”. Anything larger is still an “unfilled open area”.
1 Like
A bit too restrictive. An established eye can still be a bit larger, as long as the opponent can’t make an eye inside.
1 Like