 There is, in the second place, the assumption that the axioms of pure quantificational logic remain true when we expand the language to include other sentential operators, whether temporal, modal or  otherwise.[27]  What is perhaps the most common response to our predicament is to recoil from pure quantificational logic into a suitably weakened variant of it. This is, for example, the path taken in Kripke (1963), where Kripke proposes to weaken the axiom of universal instantiation in line with the first version of inclusive quantificational logic discussed earlier. Since \(\exists y(x = y)\) is not a theorem of inclusive quantificational logic, we are not in a position to necessitate, which blocks the derivation of the necessity of  being.[28]  Kripke’s quantified modal logic is discussed in the entry on the  possibilism-actualism debate.  Others have fallen back into alternative forms of free logic, but there appears to be no consensus as to which one is the best alternative to pure quantificational logic. It may be helpful to note, however, that some of the relevant free logics merely restrict the axiom of universal instantiation by means of an existence predicate and do nothing to block the derivation of other allegedly problematic principles such as the necessity of identity, which is the thesis that everything is necessarily self-identical. Since, presumably, an object can only be necessarily self-identical if it exists necessarily, opponents of CBF will also want to have some resources to block the necessity of identity.