R#, P#) be standard models satisfying the following conditions.
(1) W# = WiJ X, where X is a set disjoint from W.
(2) i?# = R U <S, where S is a binary relation on W# for which
it holds that aeX whenever aSft.
(3) P# = P.
is said to be a safe extension of *4t - safe in the sense that, since
R# does not lead from W into X, truth values of sentences at worlds
common to J( and J(# are the same in both models. That is, for every
a
The proof of this is by induction on the complexity of A. Give it at least
Post too long. Click here to view the full text.