What is the story of "self-contradiction"?

Self-contradiction is from Han Fei Zi, which is about a man in Chu who sold spears and shields, saying that his shields were so strong that no spear could penetrate them, and that his spears were so sharp that no shield could penetrate them. When an onlooker asked, "What would happen to your shield if you stabbed it with your spear," the man had no answer.

Later used to describe inconsistent behavior or speech. It also refers to incoherent character or mood. It is also used to describe the inconsistency of a person's words and actions.

Expanded:

Contradictory: Spear, a long spear, a thrusting weapon for attacking an enemy; Shield: A shield to protect oneself.

Subject-predicate tense; used as predicate and determiner. Cannot be used for more than two parties, but only for a single self-contradiction.

Example sentences:

1. Mao Zedong, "On the Long War:" "Isn't it self-contradictory to fight valiantly in the front and then give up the land in the back?" .

2, "Ziji Tongjian - Liang Wu Di Taiqing two years": "Now the two palaces are in danger, and the cunning invaders are monstrous, the ministers should work together, how can they be self-contradictory?"