Difference between revisions of "Russell's Paradox"

 
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This paradox, due to Bertrand Russell, was one of those which forced the axiomatization of set theory. We start with the property <math>P</math>: (<math>x</math> does not belong to <math>x</math>). We define <math>C</math> to be the collection of all <math>x</math> with the property <math>P</math>. Now comes the question: does <math>C</math> have the property <math>P</math>? Assuming it does, it cannot be in itself, in spite of satisfying its own membership criterion, a contradiction. Assuming it doesn't, it must be in itself, in spite of not satisfying its own membership criterion. This is the paradox.
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The '''Russell's Paradox''', credited to Bertrand Russell, was one of those which forced the axiomatization of set theory.  
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Paradox
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We start with the property P: (x does not belong to x). We define C to be the collection of all x with the property P. Now comes the question: does C have the property P? Assuming it does, it cannot be in itself, in spite of satisfying its own membership criterion, a contradiction. Assuming it doesn't, it must be in itself, in spite of not satisfying its own membership criterion. This is the paradox.
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See Also
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*[[Set]]
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[[Category:Set theory]]

Latest revision as of 17:57, 12 May 2023

The Russell's Paradox, credited to Bertrand Russell, was one of those which forced the axiomatization of set theory.

Paradox We start with the property P: (x does not belong to x). We define C to be the collection of all x with the property P. Now comes the question: does C have the property P? Assuming it does, it cannot be in itself, in spite of satisfying its own membership criterion, a contradiction. Assuming it doesn't, it must be in itself, in spite of not satisfying its own membership criterion. This is the paradox.

See Also