al for you is (I take it) something like
&gt; &gt; a 4D chunk of space-time, while the extension of a set is the set of
&gt; &gt; its members (i.e., the set itself).
&gt;
&gt; MW: Correct.
&gt;
&gt; &gt; Granted, for you, both types of extension are used to individuate
&gt; &gt; objects of the relevant sort, but to avoid confusion perhaps it's
&gt; &gt; better to talk instead about, e.g., the spatio-temporal *extent* or
&gt; &gt; *boundaries* (or the like) of an individual, rather than its
&gt; &gt; extensi