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Barber & Russell Paradoxes (History of Undecidability Part 2) - Computerphile
Key Facts In This Video
One theory of "two" is that the essence of twoness is the union the set of all sets with two members, like black and white. 02:12
Bertrand Russell showed that some attempted formalizations of the naive set theory were contradictory. 03:40
The Russell's paradox deals with the idea that mathematics is not always decidable. 09:18