Eye versus No Eye Capturing Race

One eye versus no eye  

At first glance Black seems to have more liberties than White (6 against 5). When we apply the theory, however Black cannot win the race even if playing first. a + b + circled points yields 5. The c points yield 4.

Second example

There is a second way in which eyes influence semeais, less well-known (and in general also less important). The following diagrams show how it works. Black and White both have four dame.

No shared liberties  

Black has an eye and White does not, but at first sight that does not seem to matter, because there are no shared liberties. Nevertheless, White is not able to win the capturing race, as this diagram shows.

The reason for this is the approach move that White has to make, with . At first sight, Black has a similar approach move problem at a. However, this problem does not worry Black, who can simply solve it by making b the last liberty that Black fills up. White, on the other hand, is forced to play the eye as the last move - so White has to make the approach move first. Stating this as a rule:

Rule

If there are no shared liberties in a semeai, each player can omit the necessary approach moves for one liberty, but not if his/her opponent has an eye.