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Collections are not necessarily a set

Author:      yendor
I heard that not every collection of objects is a set.  I was wondering if
you could give an example of such a selection collection, and explain why it
is not a set.

Response #:  1 of 1
Author:      jlu
I have also seen such a remark made in very pedantic math books.  I think
the idea is to avoid the "set of all sets" paradox.  That is, the collection
of all sets is not a set.  That is because "set" does not properly describe
a property of a "objects" that can be collected into sets.  Ordinary mortals
need not worry about the distinction.

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