re at different
levels and one is made out of the other.
&gt; 
&gt; &gt; &gt;
&gt; &gt;&lt;snip&gt;
&gt; &gt; &gt;
&gt; &gt; &gt; &gt;
&gt; &gt; &gt; &gt; &gt;
&gt; &gt; &gt; &gt; &gt; Set
&gt; &gt; &gt; &gt; &gt;
&gt; &gt; &gt; &gt; &gt; Contains axioms and relations that apply to all mathematically
&gt; &gt; &gt; &gt; &gt; defined sets.
&gt; &gt; &gt;
&gt; &gt; &gt; The idea of a 'mathematically defined' set is a bad idea. 
&gt; There is no
&gt; &gt; &gt; clear category of a mathematical definition (as op