[Welcome to Sensei's Library!]

StartingPoints
ReferenceSection
About


Paths
LifeAndDeath
EyesCollection
KillingShapes
Principles

Referenced by
Eye
LibertyIntroductory
BentFourInTheCorner
Base
AlmostFill
Alive
Dead
CarpenterSSquare
BentFour
GeneralEyeDefinition
PlayOnThePointOfS...
EyeDefinitionDisc...
TwistedFour
BeginnerStudySection
BigEyeLiberties
ThreeInARow
BentThree
Killing
Capturing
SmallestGroupWith...

 

Two Eyes
Path: EyesCollection   · Prev: Eye   · Next: RealEye
Path: LifeAndDeath   · Prev: Eyes   · Next: EyeSpace
Path: Principles   · Prev: Liberties   · Next: Connection

  Difficulty: Introductory   Keywords: Life & Death

To be safe from capture, a group of stones must in general have two eyes (or, to put it more clearly, be able to make them in response to any threat). This is the primary way to make groups alive (the other, usually less desirable way is seki).

The basic rules of go state that when a group's last liberty is removed, the group is captured. It follows that, if a group has at least two liberties which cannot be removed, then the group cannot be killed and is alive. All subtleties aside, such an unremovable liberty is what we call an eye.

[Diagram]
Example

Look at the circled points. A white stone placed on any of them would be disconnected from her own stones and would have no liberties. Both Black chains would still have the other circled point as a liberty. Such a White move would thus be illegal. Neither of the two circled points can be occupied without the other. In conclusion, the circled points are two unremovable liberties of the Black group, or two eyes and it is impossible to remove the Black group from the board.




Authors

  • Morten Pahle
  • StevertIgo
  • Dieter: Rather than a WME, I completely revised this page. There were both incorrect statements and too technical comments on it for a basic explanation. I avoided technical issues by including "generally speaking". Check out the [ext] previous version and recover what was left out unjustified.


Path: EyesCollection   · Prev: Eye   · Next: RealEye
Path: LifeAndDeath   · Prev: Eyes   · Next: EyeSpace
Path: Principles   · Prev: Liberties   · Next: Connection

This is a copy of the living page "Two Eyes" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.