Life and death

Life and death (死活) is a fundamental concept in the game of Go, where the status of a distinct group of stones is determined as either being "alive", where they may remain on the board indefinitely, or "dead," where the group will be lost as "captured". The basic idea can be summarized by:

The concept of Life and death is a consequence of two basic Go rules.

Because of these rules, some groups can never be captured (alive), while others can't avoid capture (dead).

The group at a is not alive, but may become alive, so is unsettled. The group at b is dead. The group at c and d is alive.

See the diagram on the right, and suppose white tries to capture the black groups:

The black group surrounding c and d can never be captured, and is called alive. The group can live because it has two—separated—inner liberties, where white can't play. A group such as b that cannot become alive is called dead. Groups that are neither alive, nor dead, are called unsettled.

e and f are eyes, g is a fake eye.

Liberties inside a group are called eyes. In the previous example, a, b, c and d are eyes. An eye may be a single empty intersection, or more of them. In the diagram on the left, the intersections marked e form a single eye, and f forms another eye. The group has two—separated—eye spaces. Even though white can make a move in these eyes, black could eventually capture the white stones, and each eye would thereby be reduced to a single intersection.

An inner liberty where the opponent can still play, by capturing part of the group that encloses this liberty, is called a 'false eye' or 'deficient eye'. In the example on the left, white can play at g, and capture a black stone. The eye is then destroyed, and black has only one eye left. A group with only one eye is not alive. The black group at g is dead, because it can not form two true eyes.

Life and death situations and issues occur when an area with a group of stones surrounds a small area (<7 points) so that it may not be possible to form two separate independent "eyes". As the board fills up during the course of the game, certain groups will survive, and others may not. A group with a single eye can normally be captured, in the end, by filling first round the outside. The purpose of making two eyes is to prevent this. Novices sometimes interpret making two eyes in a narrow way, and form 'explicit' eyes one by one. This is often the wrong approach, and it is better to play generally to make a territory inside a group out of which two eyes can surely be made, if and when the opponent attacks it. Groups with seven or more points of territory can usually form two eyes when attacked, unless there are structural weaknesses.

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