notion of part, which is transitive. Where we would like to say
&gt;a whole composed of physical parts is itself physical. We have the notion
&gt;of
&gt;a member of a group (collection, or whatever), which has characteristics of
&gt;both. Note: we use member of and part of for group - and I am not sure
&gt;quite
&gt;where the differences lie (and I would be interested in finding out). It
&gt;seems we now have three options:
&gt;1. Treat groups as sets. This recognizes that 'member of group' is not
&gt;trans