 Central to probabilistic treatments of conditionals is the notion of conditional probability. Given a Boolean formula \(A\) of \(L_0\), and a set \(W\) of possible worlds over which they are interpreted, we let \(\Pr(A)\) denote \(\Pr(\lvert A\rvert)\), namely the probability assigned to the worlds in which \(A\) is true. For \(A\) and \(C\) two Boolean formulae, the conditional probability \(\Pr(C\mkern2mu|\mkern2muA)\) is definable by the Ratio Formula: