Even in modal logic, one may wish to restrict the range of possible worlds which are relevant in determining whether \(\Box A\) is true at a given world. For example, I might say that it is necessary for me to pay my bills, even though I know full well that there is a possible world where I fail to pay them. In ordinary speech, the claim that \(A\) is necessary does not require the truth of \(A\) in all possible worlds, but rather only in a certain class of worlds which I have in mind (for examp