This thesis consists of several independent papers in population ethics. I begin in Chapter 1 by critiquing some well-known 'impossibility theorems', which purport to show there can be no intuitively satisfactory population axiology. I identify axiological vagueness as a promising way to escape or at least mitigate the effects of these theorems. In particular, in Chapter 2, I argue that certain of the impossibility theorems have little more dialectical force than sorites arguments do. From these negative arguments I move to positive ones. In Chapter 3, I justify the use of a 'veil of ignorance', starting from three more basic normative principles. This leads to positive arguments for various kinds of utilitarianism - the best such arguments I know. But in general the implications of the veil depend on how one answers what I call 'the risky existential question': what is the value to an individual of a chance of non-existence? I chart out the main options, and raise some puzzles for non-comparativism, the view that life is incomparable to non-existence. Finally, in Chapter 4, I consider the consequences for population ethics of the idea that what is normatively relevant is not personal identity, but a degreed relation of psychological connectedness. In particular, I pursue a strategy based in population ethics for understanding the controversial 'time-relative interests' account of the badness of death.

Moral vagueness is encountered when the alethic value of some moral statement containing a moral predicate is deemed to be vague. One such statement could be “abortion in week 22 is permissible”. Given the metaethical framework of moral realism, there are three standard approaches to understanding the ontology of such vagueness. The semantic approach states that the vagueness is due to our language not being able to adequately refer to the moral reality. The ontic approach states that the vagueness is an intrinsic feature of the moral reality, and as such it will always persist. The epistemic approach states that the vagueness is due to subjects not being able to know the moral reality. In effect, there are things about morality we cannot know, because of our epistemic disposition. In this thesis, I investigate arguments in favor of all three approaches and find that of the three, the epistemic approach – here named moral epistemicism – has the best chances of succeeding. / Moralisk vaghet uppstår när sanningsvärdet av ett moraliskt uttalande, innehållandes ett moraliskt predikat, anses vara vagt. Ett sådant uttalande kan vara "abort i vecka 22 är tillåtet". Givet moralisk realism som metaetiskt ramverk finns det tre vedertagna tillvägagångssätt för att förstå ontologin hos en sådan vaghet. Det semantiska tillvägagångssättet hävdar att vagheten beror på att vårat språk inte kan referera till den moraliska verkligheten på ett adekvat sätt. Det ontiska tillvägagångssättet hävdar att vagheten är en inneboende egenskap hos den moraliska verkligheten, det är verkligheten själv som är vag. Det epistemiska tillvägagångssättet hävdar att vagheten beror på att vi som subjekt inte kan veta allt om den moraliska verkligheten. Det finns moraliska sanningar som vi inte kan veta på grund av vår epistemiska disposition. I denna avhandling undersöker jag argument till förmån för alla tre tillvägagångssätt och finner att det epistemiska tillvägagångssättet – här benämnd moralisk epistemicism – har störst chans att lyckas.