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The barber paradox is a puzzle derived from Russell's paradox. It was used by Bertrand Russell himself as an illustration of the paradox, though he attributes it to an unnamed person who suggested it to him.〔''The Philosophy of Logical Atomism'', reprinted in ''The Collected Papers of Bertrand Russell, 1914-19'', Vol 8., p. 228〕 It shows that an apparently plausible scenario is logically impossible. Specifically, it describes a barber who is defined such that he both shaves himself and does not shave himself. == Paradox == You can define the barber as "one who shaves all those, and those only, who do not shave themselves." The question is, does the barber shave himself?〔Bertrand Russell: ''The Philosophy of Logical Atomism'', 1918, in: ''The Collected Papers of Bertrand Russell'', 1914-19, Vol 8., p. 228.〕 Answering this question results in a contradiction. The barber cannot shave himself as he only shaves those who do not shave themselves. As such, if he shaves himself he ceases to be a barber. If the barber does not shave himself then he fits into the group of people who would be shaved by the barber (and, so, as the barber he needs to shave himself). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Barber paradox」の詳細全文を読む スポンサード リンク
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