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Sets and classes

  1. Aug 18, 2008 #1
    The stupid question of the day:

    The existence of proper classes is often proven by contradiction: assume that some object is a set, you'll find a contradiction, therefore it is not a set. We baptized those as "classes".

    Will (can) this even happen to classes? To find some object, assume it is a class, and get a contradiction, proving it is something else?
     
  2. jcsd
  3. Aug 18, 2008 #2

    Hurkyl

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    Except for the question of internal vs external in nonstandard analysis, I can't think of any situation in ordinary mathematics where such a thing could come up. The only reason we see it with sets and classes is because one of the main applications of sets is to serve as a simplified yet extensive version of higher-order logic.
     
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