A Beginner's Introduction to GOA Beginner's Introduction to GOThe first thing that every Go player must learn, after the rules, is
how to tell when stones are alive and when they are dead. Life-and-death
struggles between enemy stones happen all the time, and they are one of
the most interesting parts of the game.
In Figure 21, above, the black stones have an eye at A. (An eye is a
single liberty surrounded by a string of stones.) As we saw before, White
cannot play a stone into this eye because of the suicide rule, unless White
first plays a stone at B to put the black stones into atari. Then White
would be allowed to play inside the eye and capture the black stones. Since
Black can't stop White from playing B and then A, these black stones are
dead. But what if there are two eyes?
In Figure 22, above, the black stones have two eyes. White can't play
at C because that would not capture the black stones (they would still have
another liberty at D). But White can't play at D either, for the same reason.
So these stones are alive, and there is no way for White to ever capture
them. This gives us the most important principle in the game of Go:
In actual games, things usually get a bit more complicated. Often, a
player's stones will not all be connected together as they were in Figure
22. Instead, there will be several strings of stones gathered close together
to form a group of stones. Sometimes these groups can form two eyes, and
be alive. But something that looks like an eye may turn out to be a false
eye if the stones are not connected, and the stones may be dead instead
of alive.
In Figure 23, all of the groups of black stones are alive. Although each
group is made up of two or three separate strings of stones which are not
actually connected, each of these strings has two or three liberties, and
White cannot capture any of them. The important thing is that each string
of stones must help to form at least two of the eyes, and thus be protected
from capture. But if any string of stones is next to only one eye, then
those stones are not safe from being captured, and that eye is called a
false eye.
In Figure 24, the black groups look like they have two eyes, but they
don't. The stones marked with X's are protected by only one eye (marked
with an A), and in fact they are already in atari. White can play A to capture
the marked stones, and so A is not a real eye, but only a false eye, and
all of these groups of black stones are dead. You may think that there are
ko fights in the last two groups, but these are not real ko fights, either,
because Black has no way to win them. If Black plays at A to save the stone
marked X (the usual way to win a ko fight), that will just put more of the
black stones into atari (and give White an extra captive, too). In the last
example, B also turns out to be a false eye, because some of the stones
around it are not next to any other eye (A is not an eye, remember). This
sort of chain reaction is common. If an eye turns out to be a false eye,
then it no longer protects the stones next to it, and this may make other
eyes that are next to those stones false, and so on. Every stone in a group
must be protected by two real eyes.
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