 to other objects will not
necessarily be time-dependent. The axioms might look very similar
in many cases, except for an explicit time point or time interval 
in assertions about objects in the real world.  Is there some
logical contradiction in believing that we can have both time-
independent definitional axioms and time-dependent assertional
axioms?

&gt; When the properties of something change with time, does one 
&gt; indicate this by referring to the time at which they hold, or does 
&gt; one regard 