Mencius uses archery and carpentry metaphors. Master Yi demands full bow draws; master carpenters stick to compass and square. Moral cultivation likewise needs strict objective standards and the highest striving for perfect virtue.
Pang Meng studied archery under Yi and mastered all of Yi’s techniques. He then thought, “In the whole world, only Yi surpasses me. If I don’t eliminate him, I’ll never be supreme.” So he killed Yi.