Self-contradictory
In ancient times, there was a man who sold spears as well as shields.
古时候，有一个人，他既卖矛又卖盾。
One day, he hawked his wares at the market and was very pleased with himself.
一天，他在集市上叫卖，非常得意。
He held up a shield and said: "My shield is very strong.
他举起他的盾说:“我的盾非常坚固。
No matter how sharp a spear is, it cannot pierce my shield."
无论怎样好的矛，都戳不穿它!”
After that, he held up his spear and bragged: "My spear is very sharp.
说完，他又举起他的矛夸口说:“我的矛非常锋利。
No matter how strong a shield is, my spear can pierce it.
无论怎样坚固的盾都能戳进去!”
When the people standing by heard this, they laughed up their sleeves.
站在旁边的人听了，都暗暗地发笑。
One of them asked him: "According to what you said, your spear is the sharpest.
有人问他:“照你这样说，你的矛是最锋利的。
No matter how strong a shield is, your spear can pierce it.
无论怎样硬的盾都戳得进去。
Your shield is also the strongest.
你的盾又是最坚固的。
No matter how sharp a spear is, it cannot pierce your shield.
无论怎样锋利的矛，也别想戳进去。
Now, if I poke your shield with your spear, what will be the result?"
那么，现在我用你的矛来戳你的盾，看看结果会怎样呢?”
The man was so embarrassed that he could not utter a single word.
那个人窘得连一句话也答不上来。