 Even if Rachels were correct that Smith’s and Jones’s behavior is morally equivalent, we may not be able to infer the moral equivalence of killing and letting die in general (where other things are equal) from this. Shelly Kagan argues that this inference assumes that “if a factor has genuine moral relevance, then for any pair of cases, where the given factor varies while others are held constant, the cases in that pair will differ in moral status” (Kagan 1988). He claims, moreover, that this assumes the Additive Assumption, the view that “the status of the act is the net balance or sum which is the result of adding up the separate positive and negative effects of the individual factors” (Kagan 1988, 259). He raises several objections to the Additive Assumption. Firstly, one might describe a pair of cases that are exactly alike except that one is a killing and the other a letting die, where the first intuitively seems far worse than the second. If this pair of cases is as good as Rachels’ pair, then either the inference is valid in both cases—to prove the contradiction that killing is both worse and not worse than letting die—or it is invalid in both cases. Secondly, one might raise the rhetorical question: why addition—rather than, say, multiplication or some other function? Similarly, Kamm (1996, 2007) defends a Principle of Contextual Interaction according to which a property can behave differently in one context than  another.[5] 