>SOME kind of relation between any two entities. Ultimately, just by being
>CONSIDERED together in the same frame is a common property.
>
>
Cliff, this is the meaning of a set, not a system. And equating "set" with
"system" leads to severe philosophical and practical confusions. Systems
Theory (the study of interrelated things) is a subset of Set Theory (the
study of groups of things), not the reverse.