 Some philosophers have not found this argument very convincing. Faye (1994) has pointed to the following problematic issues. First, Mellor measures the probability of singular events (propensities) instead of the probability of certain kinds of events. Second, he does not differentiate between circumstances in which a \(B\) is followed by an \(A\) and those in which a \(B\) is not followed by an \(A\). The argument is valid only if it can be proved, and not be stipulated, that (1) and (3) happen surrounded by the same facts. Many people would say that in a world of (1) must be different from a world of (3) in some other important respects than merely containing \(a\) or \({\sim}a\), especially since Mellor claims that the argument is valid for deterministic situations as well. Third, the equal distribution of the various chains seems quite selective. In Mellor’s G&amp;H world, in which the number of the four chains is equal, and therefore in which the probabilities are equal, there cannot be any causal relationship between the individual \(b\) and the individual \(a\) due to the fact that the occurrence of \(a\) or \({\sim}a\) happens under exactly the same circumstances given \(b\). Finally, fourth, it seems appropriate to claim that any negative argument, like Mellor’s, should be able to show that what holds true of one world can be proved to hold true of every other world similar in all relevant respects, but in which G-chains and H-chains are not equally distributed.