 As noted earlier, those with FMS have equal moral status. This entails that when two beings both have FMS, the reason not to interfere with them is equally strong, all relevant factors held equal, and so one equally wrongs them when acting against these reasons, all relevant factors held equal. This idea has been dubbed the “equal wrongness thesis” and it is open to various interpretations. McMahan (2002, p. 235) focuses on the equal wrongness of killing (rather than the more general idea of the equal wrongness of acting against all the stringent protections that two beings with FMS merit). According to McMahan, a variety of factors are thought not to affect the wrongness of killing of beings with FMS (and hence it does not matter whether they are held equal), in cases when killing is wrong: the being’s age, level of intelligence, temperament, social circumstances, etc. For example, for a young and an old person who both have FMS, the reasons not to kill them are claimed to be equally strong despite the fact that the young person stands to lose much more in dying than the old. This is consistent with holding (1) that other factors, unrelated to the level of harm to the being, such as the mode of agency, defeaters, the number of people affected, and special relationships, do make a difference to the degree of wrongness of killing; and (2) that when killing is not wrong, as well as in the context of saving, factors related to harm (e.g., age, etc.) do make a difference to what’s best to do (McMahan 2002, pp. 236–7). McMahan (2008) acknowledges that there are many challenges to the equal wrongness thesis. While the equal moral status of beings with FMS entails the equal wrongness of killing such beings when all relevant factors are held equal, one can disagree about how best to interpret it, i.e., which factors are or are not relevant to the degree of wrongness of killing beings with FMS.