Thing and Nothing

The question of the meaning of classes has come up many times.

In terms of associating real world meaning with classes,
I still think Ayn Rand (Introduction to Objectivist Epistemology)
has the best definition.
    A concept is a mental integration of two or more units
    possessing the same distinguishing characteristic(s),
    with their particular measurements omitted.

0 units => nonexistent
1 unit => an individual, not a concept
2 or more units => meaningful concept

I think of Nothing as a mathematically useful set,
not a meaningful class.

Dick McCullough
mKE do enhance od "Real Intelligence" done;
knowledge := man do identify od existent done;
knowledge haspart proposition list;
http://mKRmKE.org/