The if-clause refers to “admissible” propositions, which are roughly propositions that give no more information about whether or not \(E\) is true than is already contained in \(\Ch(E) = c\). To see why we need the qualification imposed by the if-clause, suppose for instance that the event \(E\) is “the coin will land heads the next time it is tossed”. If the conditioning proposition \(A\) is “the coin is fair”, it is a paradigmatic example of an “ordinary” proposition. This reproduces the Coin