| Position 1 | Position 2 | Position 3 |
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Since for a group to be alive it has to have two separate eyes, it just stands to reason that in order to kill a group one has to prevent it from making two separate eyes. This idea is tightly related with the concept of vital point. A vital point is the point at which one has to play to make two eyes or to prevent from making two eyes. In the group shown in Position 1 of Fig 1-1 such vital point is 'a'. If white takes this point (as in Position 2), he will kill the black group. If black takes this point (as in Position 3)- he will make his group alive.
| Position 1 | Position 2 | Position 3 |
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Below are some more examples of vital points - in each of these situations, if black plays at 'a' he will kill the respective white group, while if white plays at 'a' he will save the respective group. The point 'a' is the vital point in each of the shown shapes.
| Position 4 | Position 5 | Position 6 |
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The meaning of miai is "of the same value" or "performing the same function". It describes two points which can be played interchangeably since they both fulfill the same purpose. With respect to our discussion of life and death, the term miai denotes a situation in which a group has two (or more) vital points and thus cannot be killed even though the owner of the group does not immediately occupy one of them. The idea is that if the opponent takes one, then you can play the other, but you do not have to worry till the opponent actually takes one of the miai points - but then it is crucial that you take the other.
The simplest shape in which a group has two vital points is given in Position 1 of Fig 2-1. The points 'a' and 'b' are considered miai since it is enough for white to occupy only one of the to ensure the life of his group. Position 2 shows what happens if black tries to kill white group by occupying one of the miai points - white immediately occupies the other thereby making his group unconditionally alive.
| Position 1 | Position 2 | Position 3 |
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Position 3 of Fig 2-1 shows what happens if white fails to occupy the other miai point - and lets black get both of them instead. The result is that the white group is dead since white has no possibility any more to divide the area into two separate eyes.
The concept of miai is very important in life and death considerations. In our example above, the miai points were two vital points for making eyes. But it does not always have to be so! Sometimes the miai points have slightly different purposes - for example one point makes two eyes while the other connects to a live group - these two points are also miai because they are both performing the same function of saving the group. An example of such miai is given in Fig 2-2.
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The points 'a' and 'b' in Fig 2-2 are miai because they both ensure the survival of the marked black stones. The point 'a' creates two eyes, while the point 'b' connect to the rest of black stones. If white takes one of them - black has to take the other! Black does not need to spend a move on defending the marked stones until white plays one of the miai moves.
Caution:
Miai points are
very useful since they allow the player to switch elsewhere and play
in another area of the board without worrying about the safety of
the group which is "protected by the miai". But
there is a hidden weakness in such thinking - the opponent can
always use one of the miai points as a ko threat - a threat which is
very difficult to ignore. So be careful - miai is strength,
but it can also be a weakness - treat it with care and look ahead
for possible trouble it may cause.