The best books about reasons in ethics

There are a lot of great books about metaethics and a lot of great books about reasons, but this book nabs my top recommendation because Smith makes the topics so deceptively easy to get into and start thinking about. This is the book that I wrote my undergraduate senior thesis on that got me into studying and writing about philosophy for a living, and it is also one of the key books that everyone in my generation in my field grew up thinking about and reacting to. It also has a great balance between an overarching project that spans all of the chapters and some pretty self-contained discussions, especially in the earlier chapters, that helps the reader to focus on one question at a time while also getting a glimpse of how philosophical questions can add up to something bigger.

In this book, Korsgaard makes really forceful the question of what it is that gives morality any authority over us. She divides and surveys the space of possible answers to this question, and develops an incredibly ambitious answer that draws extensively on her interpretation of the historical philosopher Immanuel Kant and makes Kant’s own views intelligible in contemporary terms. It nabs my second recommendation not only because it is gripping and relatively easy to get into, but because, like my top recommendation, of the formative role that it has played for so many contemporary philosophers of my generation, for whom it set the standard of what questions needed to be asked and answered, and what the space of tools might be for trying to answer them.

In this book, Dancy defends the thesis that he calls Ethical Particularism, according to which there is no or virtually no important role for moral rules or principles to play either in moral explanation or in moral understanding. But more importantly, in my view, along the way he lays out in clear and persuasive terms what a powerful explanatory role reasons play in ethical theory. I include it third on my list because the idea that reasons are fundamental and explanatory of everything that has to do with morality and other forms of evaluation has come to be very important in contemporary philosophy, but I think before my own book, this is the work that has articulated this thought the most powerfully and explicitly.

In this book, Horty uses tools that were originally developed in the fields of artificial intelligence and non-monotonic logic in order to develop an explanatory theory of how reasons compete with one another. The main thing that has led contemporary moral philosophers to be so interested in reasons is that they seem to be able to compete. For example, if on the one hand, you promised your friend to keep a secret, that is a reason that counts against telling anyone else, but if the secret is that they are having an affair with the spouse of another of your friends, that is a reason that counts in favor of telling, and to figure out what you should do, it seems like we have to weigh these reasons together to see which one is more important. But very few ethicists have gotten very far in thinking about the distinctive challenges in understanding how reasons really do add up and compete with one another. Horty’s book is the first and still only really serious treatment of this question, so it belongs on any list of the most important books about reasons.

Featured prominently in the plot of the NBC comedy The Good Place, Scanlon’s 1998 book covers much more than reasons and metaethics – it offers an ambitious explanatory theory of where our moral obligations to one another come from, and why they have the particular shape that they do – including of why we can’t justify doing terrible things to someone just because it benefits many other people. But in the first two chapters of the book, Scanlon also offers a large range of important and influential arguments about the nature of reasons and their relationship to both desire and value, and those two chapters in their own right merit this book a place on this list, in addition to its many other virtues.