The single most important question about any group in Go is whether it can live. And the answer almost always depends on eyes. The vocabulary around eyes is small but precise: eye, false eye, eye space, vital point. Knowing these words, and what they describe, is the foundation of life and death.
Eye
An eye is an empty point, or small area, completely surrounded by one player's stones, which the opponent cannot fill without being captured. Because a stone placed inside an eye has no liberties, the opponent can only play there if doing so captures something.
This is why eyes make groups hard to capture: to capture a group, you must fill all its liberties, and you cannot fill an eye while the group has any other liberty.
Why two eyes mean life
A group with one eye can still be captured. The opponent fills all its outside liberties, and then the eye becomes the last liberty; a stone played in it captures the whole group.
A group with two separate eyes can never be captured. To capture it, the opponent would need to fill both eyes. But playing in either eye while the other remains is suicide, because the stone would have no liberties and would capture nothing. On this site, suicide is not allowed at all. So the two-eyed group lives permanently.
This small group is alive. Count its eyes: a1 is surrounded by black stones at a2 and b1, and c1 by b1, c2 and d1. Two separate eyes: life.
False eye
A false eye looks like an eye but is not. It happens when the stones around the empty point are not all connected, so the opponent can capture some of them and destroy the "eye".
The usual sign is the diagonal points. For an eye in the middle of the board, if the opponent controls two or more of the four diagonal points, the eye is often false. On the edge, controlling one of the two diagonal points is usually enough; in the corner, the single diagonal point matters.
False eyes are one of the most common reasons a group that "has two eyes" still dies. Before relying on an eye, check the diagonals.
Eye space
Eye space is the area inside a group where eyes can be made. A group with large eye space can usually make two eyes; a group with small or awkward eye space may not.
Some eye spaces are famous:
- Two in a row: can make only one eye; the group is dead unless it gets more space.
- Three in a row: alive if the owner plays the middle point first, dead if the opponent does.
- Four in a row (a straight line): usually alive, because it gives two ways to make two eyes.
- Bent shapes and squares: have their own rules; the square of four points, for example, makes only one eye.
You do not need to memorise every shape at once. Learn them gradually as you meet them in games.
Vital point
The vital point of an eye space is the point that decides whether the group lives or dies. If the owner plays there, the group makes two eyes. If the opponent plays there, the group cannot. In three-in-a-row, the vital point is the middle.
Finding the vital point is the key skill in life-and-death problems. Many kills are just one stone on the right point.
Alive, dead and unsettled
- Alive: the group has two eyes or can always make them, no matter how the opponent plays.
- Dead: the group cannot make two eyes and cannot escape, no matter how its owner plays.
- Unsettled: whoever moves first decides. These are the groups that matter in fights.
On this site, dead stones must actually be captured before both players pass, because the board is counted as it stands. See capture dead stones before passing.
Seki: life without eyes
A group can also live without two eyes, in seki, when it shares liberties with an opposing group and neither can capture the other. See seki and scoring.
Where to go next
Life and death is best learned by solving positions and by noticing them in your own games. When you play the computer on the home page on 9×9 or 13×13, stop whenever a group looks unsettled and ask: where is the vital point? Against people on the online page, life and death decides many games. Sign in on the account page to save and replay your games, and look back at every group that died to find the moment it could have lived.
For more vocabulary, see the Go glossary A to Z, and for the capture words, liberty, atari and snapback.
A simple way to test a group
When you are unsure whether a group lives, run a short test. First, count the empty points inside it: that is its eye space. Second, ask whether that space can be divided into two separate eyes, and where the dividing move would go. Third, imagine your opponent playing on that point first. If the group still has another way to make two eyes, it is alive; the two ways are miai. If not, the group is unsettled, and whoever plays the vital point first decides its fate.
This test takes practice, but it quickly becomes a habit. Many players find it helpful to use it on their opponent's groups as well as their own: an unsettled enemy group is a target, and knowing its vital point tells you exactly where to attack. The same logic applies to your own groups in reverse: if one of them is unsettled, playing the vital point yourself is often the biggest move on the board.
Frequently asked questions
Why does a group need two eyes?
Because the opponent can only fill an eye as the last liberty. With two separate eyes, filling either one is suicide, so the group can never be captured.
What is a false eye?
A point that looks like an eye, but the stones around it can be captured, destroying it. Check the diagonal points.
What is a vital point?
The point in an eye space that decides whether the group lives or dies.
Can a group live with one eye?
Only in special cases such as seki. Normally a one-eyed group can be captured.
Is a square of four points two eyes?
No. A square of four empty points makes only one eye.
