自相矛盾
大街上，有个卖矛和盾的人，他举起盾说：“我的盾啊，非常结实，不管多好的茅，也刺不穿它！” 说完这个话，他又举起矛说：“我的矛呀！十分锋利，不管多硬的矛，也能刺穿！”
于是，有一个人问它：“如果用你的矛来刺你的盾，结果怎样呢？” 卖矛和盾的人站在那里，一句话也回答不出来。
成语 Chéngyǔ，similar to English idiom, is a word group or a phrase which is established through usage and practice. Unlike English idiom, a Chéngyǔ is often made of a fixed number of Chinese characters, and most Chéngyǔ (98%) have four characters. Chéngyǔ often contain literary allusions which were derived from analogy or historical stories. The meaning of a Chéngyǔ is often much more difficult to derive from its constituents than an average English idiom. While some modern Chéngyǔ have a direct literal translation in other languages, many Chéngyǔ do not have a foreign language equivalent due to their strong historical background. One, who is able to master the use of Chéngyǔ, is considered as well-educated and receives respect.