Lesson 7 of 12
Life and death
3 min

Two Eyes in Go: Why a Group With Two Eyes Lives

A group lives as long as it has a liberty. Eyes are liberties your opponent can only fill last, and two of them can never both be filled. You play Black.

Step 1 of 4

Eyes
Black's group along the top has two empty points inside it, B9 and E9, marked with stars. Each is an eye: an empty point surrounded by one group's stones. White can't play in either. A white stone on B9 would have no liberties and capture nothing, so the rules forbid it, and the same goes for E9. With two eyes, Black's group can never be captured.
One eye is not enough
White's group in the top-left corner has one eye, B9, and one liberty outside, D8. A stone in the eye is suicide while the group has another liberty, so you start outside. Once D8 is filled, B9 is White's last liberty, and a stone there captures.
Your move
Capture White's group: fill its outside liberty, then the eye.
Make a second eye
Your group has one eye, A1. Two more points are inside it, C1 and D1, but D1 touches White's stone on E1. If White plays D1, C1 can't become an eye, and your group is left with one. Make your second eye first.
Your move
Make your group live with two eyes.
Two points, one eye
White's group in the corner has two empty points inside it, B9 and C9. Is it alive?
Question

What you learned

An eye is an empty point surrounded by one group's stones.
An opponent can't play in an eye unless the stone would capture.
One eye is filled last and the group dies. Two separate eyes can never be filled.
Two points side by side make one eye, not two.