On being justifiable to others: act contractualism, numbers and justification

In my thesis, I investigate what the ideal of being justifiable to others entails for moral theory. I do that first by formulating and defending a moral view called Act Contractualism, whose structure, I argue, best fulfils the ideal of justifiability to others. Second, I ask what considerations contribute to making an act justifiable, both to formulate a theory of reasons for objection to ground my act contractualist view, and to use a contractualist approach to inform broader discussions on Partial Aggregation. In the first half of my project (chapters 1, 2 and 3), I carve out conceptual space for Act Contractualism by showing that one can meaningfully formulate an act-based contractualist view which is neither conceptually mistaken nor extensionally equivalent to Rule Contractualism, and which is appropriately supported by a contractualist rationale. I then show that Act Contractualism is uniquely placed to address important objections raised against other moral views. The outcome is a view which is both grounded in an appealing rationale and extensionally adequate with respect to a variety of problem cases. In the second half of my project (chapter 4 and 5), I look at what the contractualist ideal of justifiability to others entails in cases involving numbers. My co-authors and I first engage with the literature on Partial Aggregation to show that a key contractualist feature called the Individual Restriction, which is meant to secure justifiability to individuals, prevents Contractualism from yielding plausible results in these cases. We argue that contractualists should exercise caution when appealing to this restriction and might even want to abandon it. We then focus on a type of cases involving both very strong claims and very small claims to ask whether the presence of the latter can justifiably make a difference to whom we ought to save.