In arguing for the theoretical need to distinguish the justifying and requiring roles of practical reasons, some of the work in the previous three chapters was devoted to arguing that we can take certain commonsense normative claims at face value. Among those claims were, for example, that being immoral is not necessarily irrational, but that making sacrifices for other people is not irrational either; that it is irrational to refuse to take medicine that will restore one to perfect health and a happy life, regardless of one's indifference to that prospect; that simply having a strong desire for things like pain or disability does not, by itself, give one the slightest reason to pursue them. This chapter will take these sorts of claims for granted. The point here is to argue in a more formal way against views that attribute a single strength value to practical reasons, and that go on to claim that the rational status of an action is dependent only on the strengths of the reasons that favor and oppose it. Once this is demonstrated, the second half of the chapter will then go on to argue that the justifying/requiring distinction explains the relevant phenomena better than do two other proposals: incommensurability of reasons, and a technical device called an ‘exclusionary permission.’ In this chapter, as in chapters 2 and 3, the arguments will be presented in terms of subjective rationality.