I Ching
Interpreted by wu wei

Correctness

Before a kua is formed, there are six empty places that the lines will fill. Three of the places require strong lines, meaning undivided lines, and three of the places require weak lines, meaning divided lines. The places 1, 3, and 5 are strong and require strong, undivided lines. These lines are then considered correct because they are strong lines in strong places. Places 2, 4, and 6 require weak, divided lines. These lines are then considered correct because they are weak lines in weak places. When a weak line is in a place which calls for a strong line, it is generally unequal to the task at hand. When a strong line is in a place which calls for a weak line, it is generally too aggressive for the task at hand. Keep in mind that those are general rules and can be modified according to special conditions of the kua, but any such special conditions will always be stated in the kua.