Two Eyes in Go — Why a Group Needs Them to Live | PlayGo.gg

A group of stones that cannot ever be captured.

What is two-eye life?

A stone is captured when its last liberty is filled. A group with one eye still has that point as a liberty, but the opponent can simply play inside it. The move appears illegal because you are placing a stone that has no liberties, but because you are capturing the surrounding stones in the process, that stone actually has more than 0 liberties.

Naturally, if a liberties has 2 liberties, but they are surrounded and separate, then your opponent cannot capture them because both moves would be illegal (they have 0 liberties and are not capturing anything).

Thus, any surrounded group that has 2 separate spaces (eyes) or more, is considered alive!

When are two eyes the right goal?

As a beginner, you almost always want to make 2 eyes when you are surrounded. However, a common mistake beginners make is that they will fill in their own points until they have 2 eyes. This is counter to the objective of making more points than your opponent. Distinguishing when to fill area in your own territory because there is a threat vs. when not to is a skill that requires real-game experience.

Example of two eyes in a game

Where can black play to make 2 eyes?

Making 2 eyes is as important of a rule as liberties and capturing. Please make sure you are confident with this rule and the practice puzzles before proceeding.