ppose that a formal system like {L(A), L(B)} is initially approached from
a theoretical direction, in other words, by listing the abstract properties
that one thinks it ought to have.  Then the existence of an extensional model
that satisfies these constraints, as exhibited by way of sign relation tables,
demonstrates that one's theoretical description is logically consistent, even
if the models that first come to mind are still a bit too abstractly symbolic
and lack all of the dynamic concreteness that is 