n the case of a configured group, which a football team can be
&gt;interpreted as, we have the positions, which give the team its structure.
&gt;Then substituting a team member, is just changing the person who plays in a
&gt;position. There is the same set - in the sense of the same configutation,
&gt;it
&gt;is just that one of the positions - a space-time worm - has different
&gt;people
&gt;occupying different stages at different times. So in a perdurantist
&gt;world-view we can explain what you mean by a 