 The modal schemas  K  and  T,  with their simple modalities, are unaffected by MSA but not so for the schemas  4,  B, and  5,  all three of which involve nested modalities. The example of \(\Box(\sfL\sfp \to \sfL\sfp)\) above motivating NecA has already shown that singular necessities might not themselves be necessary and, hence, serves as well to illustrate the invalidity of 4: \(\sfL\sfp \to \sfL\sfp\) is true at all possible worlds, and hence, necessary, \(\Box(\sfL\sfp \to \sfL\sfp)\); but \(\Box(\sfL\sfp \to \sfL\sfp)\) fails to be true at Prior-free worlds and, hence, is not itself necessary, i.e., \(\neg\Box\Box(\sfL\sfp \to \sfL\sfp)\). B’s invalidity is illustrated by any contingent singular truth; that Prior is a logician, say, \(\sfL\sfp\). By MSA, \(\sfL\sfp\) is not possible at Prior-free worlds, and, hence, it is not necessarily possible, \(\neg\Box\Diamond \sfL\sfp\). And, of course, since it is also in fact possible that Adams is a philosopher, \(\Diamond \sfL\sfp,\) the same example shows that 5 is invalid.