楚人有鬻盾与矛者,誉之曰:“吾盾之坚,物莫能陷也。”又誉其矛曰:“吾矛之利,于物无不陷也。”或曰:“以子之矛陷子之盾,何如?”其人弗能应也。夫不可陷之盾与无不陷之矛,不可同世而立。
There was a Chu man who sold shields and spears. He boasted, "My shield is so strong that nothing can penetrate it." He also praised his spear, saying, "My spear is so sharp that it can pierce anything." Someone said, "How about using your own spear to stab your own shield?" The person could not respond. A shield that cannot be trapped and a spear that cannot be trapped cannot coexist in the same world.