Self-Contradictory: Spear-Shield 自相矛盾：以子之矛，攻子之盾

What happens when an irresistible force meets an immovable object?
An example of this contradiction is found in the origin of the Chinese word for contradiction (maodun, literally means ‘Spear-Shield’).

This term originates from a story in the 3rd century BC philosophical book Han Feizi, which led to the proverb of ‘zixiang maodun’ or ‘self-contradictory’.
A man from the State of Chu was selling his spear and shield. He pointed at his shield and shouted: ‘It is the firmest, soundest, strongest shield in the world; nothing can thrust through it regardless of how sharp it is.'

He then held the spear and said, ‘My spear is the sharpest one in the world, and it can thrust through any object no matter how firm the object is.’

An onlooker asked: ‘How about thrusting your spear through your shield?’

The man was speechless.
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如果不可抗之力与无法撼动之物相碰，什么事会发生呢？
中国词语‘矛盾’就很好的说明了这种情形。

这个词源自公元前3世纪的哲学书《韩非子》里的一个故事，也是成语《自相矛盾》的来源。
楚人有鬻(yù)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。