楚人有鬻盾與矛者，譽之曰：“ 吾盾之堅 ， 物莫能陷也 。”又譽其矛曰：“ 吾矛之利 ， 於物無不陷也 。”或曰：“以子之矛，陷子之盾，何如 ？” 其人弗能應也 。夫不可陷之盾與無不陷之矛，不可同世而立。

A guy pitched the shields and spears at Chu, who boasted that his shields were too tough to be penetrated by anything, while also boasting that his spears were so sharp that they could penetrate everything. Someone asked him what if he tried to use his spear to penetrate his shield. That guy was unable to answer the question. Well, the impenetrable shield and the spear that could pierce everything could not coexist in this world.