2.3 Basic Problems of Territory Rules (Examples)

2.3.1 Unconditional Death of Bent Four in the Corner (Elimination of Ko Threats)

Dia. 2-1 shows the bent four in the corner, which has long been considered unconditionally dead in Japan. If White plays first the result is a ko. If Black plays first he can only use the position as a ko threat; he cannot live. If White eliminates all ko threats before attacking, Black will be unable to fight the ko and will die. That is the justification generally given, but it is extremely imperfect. In Dia. 2-2, Black has a ko threat at 1 that White cannot remove. The preceding justification is absurd, because in some cases all ko threats can be removed but in other cases they cannot. You should verify that by playing 1 as a ko threat and sacrificing two stones, Black can save the group in the upper left. If a bent four in the corner is not unconditionally dead, who wins the game in Dia. 2-2, and by how many points?

Dia. 2-1	Dia. 2-2

Dia. 2-3 shows a bent four in the corner in which the surrounding white and black groups are involved in a double ko. Making the black group on the right side also die through collapse of the seki is hard to accept.

Dia. 2-3

The rule that a bent four in the corner is unconditionally dead is unnatural and no logical explanation can be given for it. New rules proposals will have to exclude this rule.