Jourdain’s paradox (1913).
Named after its discoverer, the mathematician Philip Edward Bertrand Jourdain (1879-1919).
The paradox is equivalent to the sentence ‘The second part of this sentence is true and the first part of this sentence is false’, which contradicts itself whether the first half is true or not. However, the halves of the sentence refer indirectly to themselves, so any rule prohibiting statements that refer to themselves resolves the paradox.
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