 Two further important modifications to the framework of SQML follow from Kripke’s Quinean conception of the purely general nature of logical truth. First, individual constants have no place; since there are no individual constants in any axioms, there are none in any theorems. Hence, it is not possible to reason with them in Kripke’s system. Consequently, Kripke restricts his semantics to languages with no individual  constants.[61]  Second, under the Quinean conception, the manner in which quantifiers and modal operators are introduced into proofs needs serious revision. For example, the proposition \(\forall \sfx(\sfF\sfx \to \sfF\sfx)\) is valid in KQML. In SQML, it is proved by deriving the tautology \(\sfF\sfx \to \sfF\sfx\) and applying the rule of Generalization: