Chapter 2 draws out the structural analogy between science and ethics: the idea that just as scientific theories can be underdetermined by the empirical data, so moral theories can be underdetermined by our considered judgments or intuitions. I start with the notion of a moral theory. I introduce what I take to be an independently plausible view that ascribes two functions to moral theories: accounting for our considered judgements or intuitions and explaining them. I then go into the details of both functions. I discuss the standard view of how theories are supposed to account for our considered judgements, the deductive principles model, and introduce two modifications. I then outline how the notion of grounding can be used to elucidate how many ethicists think of moral explanation. The second section is about the analogs of the data of scientific theories. I outline why I take these to be considered judgments or intuitions and why they need to be about particular cases. The third section considers two possible problems with the analogy, one stemming from the fact that ethicists also have intuitions about general principles, the other having to do with theory-ladenness.

Chapter 7 discussesa novel position in metaethics that the skeptical argument might give rise to: constructive deonticism. This position is structurally analogous to one of the most discussed anti-realist positions in science, Bas van Fraassen’s constructive empiricism. I start with an overview of van Fraassen’s view, discussing both its most important features and how it relates to its main rivals, scientific realism and logical positivism. Next, I flesh out the new position in ethics, focussing on the pragmatic understanding of moral explanation that it entails. Following this, I discuss how constructive deonticism should be classified as a metaethical position. I show that it is clearly not part of the expressivist family and at most half error theory (or fictionalism). However, the position is arguably not what realists are looking for either, instead prompting us to rethink how the metaethical realism debate has been framed. Finally, I point out what I consider to be the two most important challenges, i.e., whether we can draw such a sharp distinction bewteen deontic and explanatory claims and whether the position is a stable one.

Chapter 4 looks at two recent projects that aim to establish far more radical conclusions than Parfit, so-called consequentializing and deontologizing. Proponents of these projects try to come up with a simple mechanism to produce deontically equivalent counterparts to any consequentialist or non-consequentialist theory. I first explain how the two projects work on a technical level, that is, what steps are required to achieve deontic equivalence. I then reject several interpretations of the results of these projects, from the idea that we are all consequentialists (or deontologists) to the idea that consequentialism (or deontology) turn out to be empty traditions. Finally, I introduce the underdetermination interpretation of these projects and argue why it is to be preferred to yet another interpretation, the notational variants interpretation. If consequentializing and deontologizing can be interpreted in this way, we are presented with a much more far-reaching version of moral underdetermination.