## ABSTRACT

In other words, as Figure 15 shows, when 'Q' is false the truth value - truth or falsity - of 'Q' and 'u' does not settle the truth value of 'Q:=)U'. SO if 'Q:=)U' is true when 'Q' is false, something else must make it true. This may be something about other possible worlds, but it must also be something about this one. For since by hypothesis 'Q:=)U' is true in our world, and so states a fact about it, that fact should be entailed by the existence or non-existence in our world of one or more facta. And when 'u' is an instance of 'ch(P)=p' we have already seen in one case what the facta are.