Eye

An eye is an empty point or connected region surrounded by stones of one player. The surrounding shape makes it impossible—or impractical—for the opponent to occupy the space without self-capture. Eyes provide internal liberties and are the fundamental basis for judging a group’s life status and reading life-and-death positions.

A group with two separate true eyes is normally unconditionally alive, because the opponent cannot fill both eyes. A single eye may still be vulnerable to reduction, invasion, or a capturing race. A true eye differs from a false eye: a false eye looks enclosed but can legally be occupied because the surrounding stones do not fully protect it. An apparent eye is therefore not necessarily true, especially if the opponent can exploit a diagonal weakness or a capturing sequence.