Two Eyes Can Die

  Difficulty: Beginner   Keywords: Life & Death

Beginners may have several misunderstandings regarding eyes and eyespaces. These misunderstandings can lead beginners to believe that it is possible for a group with two eyes to die. Let's explore this:

[Diagram]

Two eyes

To be safe from capture, a group of stones needs two irremovable liberties. This is achieved by having two eyes. There are a few, comparatively rare exceptions, such as the situation described by the term two headed dragon.

In the example, the eyes are real eyes of size 1, in which the opponent cannot come. The situation becomes a little more difficult when the eyes are really eye spaces. If the player allows the opponent to play freely inside one of the eyespaces of a group, the status of the group may change.

[Diagram]

Seki - eye in the belly

Let's take this group for discussion:

[Diagram]

Seki - eye in the belly

In this example, Black has played three moves inside of one of the White group's eyes. These moves have removed all but one of the liberties within that eye of the White group. Moreover, they enclose an empty point. This is called an eye in the belly.

The white group is still alive, but it is now tangled up in a seki with the black stones in its belly: if either player plays a, the other will capture the stones linked to it.

Let's take a more extreme example, which may go wrong for beginners.

[Diagram]

Big eyespaces

This White group is considered alive: it has one eye in the corner and a big eye space next to it. Technically, this eye space can be occupied with black stones, in a way that captures all white stones:

[Diagram]

Black captures at B1

But such an event is very unlikely to occur, because of alternating play. White would have passed (or tenuki) up to 12 times in a row to get captured.


See also


This is a copy of the living page "Two Eyes Can Die" at Sensei's Library.
(OC) 2014 the Authors, published under the OpenContent License V1.0.
[Welcome to Sensei's Library!]
StartingPoints
ReferenceSection
About