![]() StartingPoints Aliases (info) Paths Referenced by Homepages
|
Liberty
Path: GiveMeLiberties · Prev: LibertyIntroductory · Next: ShortageOfLiberties
Keywords: Tactics, Go term
Liberty has two different, but related meanings in English. The first sense of liberty is an empty point adjacent to a single stone or chain of stones. In a legal position each chain has at least one liberty. This is the basic meaning. Such a liberty is called a dame in Japanese. The liberty - introductory page explains some of the more basic implications in fighting. Liberty in Chinese is 气 ("Qi" in pinyin), which literally translates to "breath".[1] The thought is that stones need breathing space and that once the last breathing space is removed, the stones die.[2] A stone or chain may be captured by filling all its adjacent points. Such captured stones are removed before the end of the turn, leaving a legal position. No stone or chain having no liberty is allowed to remain on the board between turns. A stone or chain with just one liberty is said to be in atari. It may be captured on the opponent's next move.
Each of White's stones or chains has a liberty, which is marked. They are not yet captured, and remain on the board.
However, they each have only a single liberty.
Each of these White chains has multiple liberties and is safe from capture for at least two of Black's moves. The second sense of liberty, important for tactics, is a play required to capture a single stone or chain of stones.[3] This is the sense you require if you want to say that the number of liberties measures time to capture a group. There are stones that cannot be captured, e.g. stones that are part of groups with two eyes. No number of moves is enough to capture them, they are alive. There are also stones in atari, with no way of saving them. They can be captured with one move. In between there are stones with multiple liberties which may be involved in races to capture. The easiest liberties to see and count are liberties in the first sense, or dame. The opponent must make at least as many moves to capture a stone or chain as it has dame.
Each marked chain obviously has 3 liberties. It will take Black 3 moves to capture the White chain and likewise, it will take White 3 moves to capture the Black chain. The first player wins this race.
While each marked chain appears to have only 2 liberties (in the sense of moves to capture them), they each really have 3. Black must connect at the marked point on the edge of the board, while White must take off
Here again, the first player wins.
The assessment of the necessary moves can get very complicated. For instance, a one-eyed group is often less close to capture than you'd think. Here is an example where a big eye has more liberties than are apparent.
Black appears to have only 4 liberties, but actually has 5, the same number as White. This is also a first player win - details in the footnote[4]. The number of moves to capture is normally one more than the number of moves to put into atari, but even then there are comments to make:
The player with the move can capture the other's stones.
In this seki, or standoff, the opposing chains share two dame, but there are no moves to capture. Whoever approaches puts himself in atari.
Black to play can take the ko at a, threatening to capture White's stones. White to play can make an approach move, say at b, to convert to a regular ko. Such a ko is called an approach ko.
Black plainly has 3 moves to capture, but how do we count White's?
Further reading
Authors
[1]
This is the same "Qi" as the one considered to be beneficial in terms of Feng Shui. [2] Bill: Is breath (Chinese) also ambiguous? Or does it only refer to adjacent points? unkx80: This 气, or breath as you call it, can be as ambiguous as liberty. [3] This sense may be extended to discussion of groups of several chains, to help answer the question 'how many plays does it take to capture that group?' This is actually a considerably more advanced question, which cannot so simply be answered by inspection. See secondary liberties discussion. -- Charles Matthews
After
Black just wins the race.
After
but White fills it right away. Path: GiveMeLiberties · Prev: LibertyIntroductory · Next: ShortageOfLiberties This is a copy of the living page "Liberty" at Sensei's Library. ![]() |