 Craig uses a similar, intuitive notion of “smaller than” in his argument concerning the library. It appears that the set \(B\) of red books in the library is smaller than the set \(A\) of all the books in the library, even though both have the same (infinite) size. Craig concludes that it is absurd to suppose that such a library is possible in actuality, since the set of red books would simultaneously have to be smaller than the set of all books and yet equal in size.