Reductio ad absurdum beautifuly used

Theorem:
Not all problems can be solved.

Proof:
Suppose all problems can be solved (1).
We consider following problem P:
“To find one problem which can not be solved”
Because all problems can be solved therefore we can not find this problem. It means problem P can not be solved. It contradict (1) therefore “not all problems can be solved”.

The theorem is proved.

By Quang Tuan Bui

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