Moral indeterminacy is not the same thing as moral vagueness. In this chapter, I reserve the term “indeterminacy” for phenomena that are indeterminate but not vague. The term “vagueness” is reserved for entities that are susceptible to a sorites series. The distinction between moral indeterminacy and vagueness mirrors an analogous distinction between two versions of the gradualist hypothesis. According to the first, some acts are somewhat right and somewhat wrong in the indeterministic sense; according to the second, some acts are somewhat right and somewhat wrong because they display moral vagueness. These hypotheses must be kept apart because they sometimes entail different practical verdicts. The first aim of this chapter is to clarify the notions of moral indeterminacy and vagueness that are central to these two versions of the gradualist hypothesis. The second aim is to discuss reasons for believing that morality is vague, or indeterminate but not vague, or both, and whether we should understand all these views as ontic, semantic, or epistemic theories.

If every act is either right or wrong simpliciter, a morally conscientious agent is rationally permitted to perform any of the right acts but none of the wrong ones. But what should a morally conscientious agent do when faced with a choice between options that are somewhat right and somewhat wrong? Five possible decision criteria are discussed. According to the maximizing criterion, it is rationally permissible to perform act a if and only if no option is right to a greater degree. The liberal criterion holds that it is rationally permissible to perform every act that is not entirely wrong, and the threshold criterion asserts that is rationally permissible to perform an act just in case it is not more wrong than right. The gappy criterion holds that if an act is neither right nor wrong simpliciter, then there is no fact of the matter about whether it is rationally permissible to perform. Finally, the probabilistic criterion maintains that if an act is neither entirely right nor entirely wrong, then the act is rationally permissible to perform if and only if it is chosen randomly with a probability that reflects its degree of rightness.

Chapter 2 considers legal uncertainty in the jus ad bellum as defined in the UN Charter and other sources of law. It describes paradigms, framing this law around ‘plain cases’ of lawful and unlawful force. Supervaluationism describes paradigms as determined not by one but several tests, overlapping but not co-extensive - cases may meet all or only some tests. Fuzzy logic refutes binary distinctions between lawful and unlawful force, arguing these are end-points of a continuum, separated by a ‘penumbra of uncertainty’. The chapter outlines ‘hard cases’ of force, different to cases the UN Charter most obviously prohibits: anticipatory self-defence, pre-emptive self-defence, self-defence against non-state actors, humanitarian intervention, use of force to prevent WMD proliferation. The chapter describes how interviewees and survey participants evaluated such justifications, the results displaying the vagueness already identified. The chapter identifies one possible explanation: lawyers align with different ‘interpretive cultures’, holding different opinions about valid legal tests and interpretive techniques. ‘Restrictivists’ prefer ‘formalist’ interpretation techniques, while ‘expansionists’ prefer ‘dynamist’ interpretation techniques.

Chapter 2 surveys established research showing that symmetric semantics, as described in Chapter 1, can be applied to an asymmetric metaphysics.

One way in which we might approach the challenge posed by the Sorites Paradox is considering that Sorites-susceptible predicates have several candidate extensions, or several ways in which these expressions can be made precise. For example, a candidate extension for the predicate ‘is a baby’ is the set of humans of less than two years, but also the set of those less than two years and one second, and of those less than two years and two seconds. In this chapter we present and discuss two theories for vague predicates based on this idea: super-valuationism and subvaluationism. The chapter is structured in three parts. The first presents the super- and subvaluationist theories: their similarities and differences in the semantics, the resulting logics with their most characteristic features. The second reviews the super- and subvaluationist solutions to the Sorites Paradox and provides discussion on several controversies surrounding these theories. The third part introduces proof procedures for s’valuationist logics.