tates a regularity or
a regulation that governs a whole class of situations, and
not because of its syntactic form.  So far in this discussion,
all three types of constraint are expressed in the form of
conditional propositions, but this is not a fixed requirement.
In practice, these modes of statement are distinguished by
the roles that they play within an argument, not by their
style of expression.  When the time comes to branch out from
the syllogistic framework, we will find that propositional
constrain