A long time ago in ancient China, there was a merchant who sold weapons. He would pick up a spear and advertise it as a spear that can pierce any shield. Then, he would pick up a shield and proclaim that it can block any spear. A wise man who was walking past the merchant questioned: “So what would happen if you took your ultimate spear and threw it at your ultimate shield?” The merchant could not answer.
That is why the word for contradiction, or something that does not make logical sense and cannot co-exist, in Korean, Chinese and Japanese is 모순(矛盾), meaning “spear and shield”.