A group of stones in Go lives forever if it has two real eyes, and dies if it cannot make them. An eye is an enclosed empty point your opponent cannot fill without immediately being captured, and having two of them means both points can never be filled at once.
Life and death is the single most important skill in Go. A group with two eyes is untouchable, while a group without them is only borrowing time, no matter how large it looks.
Why Two Eyes Mean Life
An eye is an empty point completely surrounded by your own connected stones. If your opponent plays into a single-eye group’s last liberty, they capture it, but if there are two separate eyes, filling one still leaves the group a liberty at the other.
To capture a group your opponent must fill its last liberty, and with two eyes they can never fill both at the same time. Playing into one eye would be self-capture while the other eye still breathes, so the move is illegal and the group lives.
Judging whether a group can live follows a clear path:
- Identify the group’s enclosed empty space.
- Ask whether that space can be divided into two separate eyes.
- Check that each eye is real, not false.
- If two real eyes exist or are certain, the group is alive.
- If only one eye is possible, the group is dead as it stands.
- Find the vital point that makes or prevents the second eye.
A large enclosed space is not automatically alive; what matters is whether it can be split into two genuine eyes.
Real Eyes Versus False Eyes
A false eye looks like an eye but fails because the surrounding stones are not truly connected. If the diagonal stones at an eye’s corners can be captured, the eye collapses and the group may die.
For an eye to be real, you must control enough of its diagonal points, especially at the edges and corners of the board. In the center you need three of the four diagonals; on the edge and in the corner you need all of them.
| Eye status | Requirement | Result |
|---|---|---|
| Real eye (center) | 3 of 4 diagonals held | Counts toward life |
| Real eye (edge) | All diagonals held | Counts toward life |
| False eye | Diagonal weakness | Fails, group may die |
| Two real eyes | Both secure | Unconditionally alive |
Count your eyes before the endgame, not after. Groups that look alive often have one real eye and one false eye, and discovering that only when your opponent strikes is far too late.
Big-eye shapes complicate matters. Some large single eyes can be reduced by the opponent to a shape that yields only one eye, so knowing the standard eye-space shapes is essential.
Eye Space and Big-Eye Shapes
The amount of enclosed space a group has determines whether it can form two eyes. A group with a large single eye space is not automatically safe, because the attacker may be able to play inside and reduce it to a shape that yields only one eye.
Certain internal shapes are "dead as they stand," meaning the surrounded space cannot be split into two eyes no matter how the defender responds. The straight three, the pyramid four, and the bulky five all collapse to a single eye if the attacker plays the vital point first.
Larger spaces flip the verdict. A group enclosing six or more points in the right shape usually has room to make two eyes even after the opponent invades, so more space generally favors life. The dividing line between living and dead shapes is one of the most studied areas of the game.
Counting eye space accurately is what separates guesswork from reading. Rather than assuming a big corner is alive, mentally place the attacker’s best invading stone and ask whether two eyes still survive. That habit will catch dangerous groups long before they collapse in a real game.
Seki: Life Without Two Eyes
There is one way a group survives without two eyes, and it is called seki, a mutual-life standoff. Two opposing groups share a small set of liberties in such a way that whoever plays first would put their own group into atari and lose it.
In seki, neither side can capture the other, so both groups live even though at least one has fewer than two eyes. The shared liberties act as a truce line that neither player dares to fill, freezing the position in place.
Recognizing seki prevents costly mistakes. A player who does not see it may throw stones into the shared liberties trying to kill, only to hand their opponent the capture instead. Once a seki is clear, both sides simply leave it alone and count the rest of the board.
Under most scoring rules the points inside a seki count for no one, and the stones themselves are alive but score nothing extra. Seki is uncommon compared with ordinary two-eye life, yet knowing it exists stops you from misreading a standoff as a group you can kill. When neither side can move without self-destructing, you are almost certainly looking at seki.
Killing and Living at Vital Points
Every unsettled group has a vital point, the key intersection that decides whether it makes two eyes. Whoever plays it first usually controls the group’s fate.
If you are attacking, play the vital point to prevent a second eye; if defending, play it first to secure both eyes. The same point often serves both purposes, which is why the race to it is so sharp.
Standard shapes have known outcomes. A straight three-space eye dies if the opponent plays the center; a bent four in the corner has its own life-and-death verdict; and the "bulky five" and "L-group" positions each carry classic results worth memorizing.
Practice with life-and-death problems, called tsumego, is the fastest way to improve at Go overall. Solving a handful daily trains your eye to spot vital points instantly in real games. Once you can reliably tell a living group from a dead one, you will stop losing whole corners and start killing your opponent’s overreaching invasions.