自相矛盾 (zì xiāng máo dùn): to contradict oneself; self-contradictory; inconsistent

自zì相xiāng矛máo盾dùn

to contradict oneself; self-contradictory; inconsistent

The seller whose spear pierced any shield and whose shield stopped any spear. 矛盾, the ordinary word for contradiction, comes straight from this story.

A Chinese idiom (成语)