Originally Posted by

**Hartlw** Start to list all sets starting with A,B,C,…

you can’t get past A:

A, {A},{{A}}, {{{A}}}, …..

Let alone A, B:

A, B, {A,B}, {A,{A,B}}, {B,{A,B}}, {A, {A,{A,B}}}, {A, {B,{A,B}}},

{B,{A,{A,B}}}, {B,{B,{A,B}}},…..

True, the fact that you can’t list them all doesn’t mean they don’t exist. However, it appears to me this construction renders the notion of “all sets” meaningless, especially if you start with A any object or concept in the universe. It's not mathematics anymore, its just words and combinations of words- philosophy (in my opinion).

And each one of these sets has a different definiton that have to be combined.