This ambitious book is a significant contribution to the study of well-being and, more broadly, to our understanding of the relationship between philosophy and science. Its clear prose and clean structure make the book a pleasure to read. The broad task of the book is described as the study of ‘well-being as an objective of science: how science should define well-being, how it should measure it, and the role of philosophy in all this’ (p. xv). The driving question behind this task is what Alexandrova calls the ‘Question of Value Aptness’: How can the science of well-being produce knowledge that is properly about well-being?

Answering the Question of Value Aptness requires grappling with both philosophical and scientific issues. Accordingly, the book consists of two parts: ‘Tools for Philosophy’ and ‘Tools for Science’. Each part consists of three chapters. (There are also two very helpful appendixes that discuss both the contemporary philosophical literature on well-being and the use of constructs across the sciences.) The first part discusses philosophical questions about the concept and theory of well-being. In the course of dealing with the nature of mid-level theories of well-being and how we can build them, Alexandrova provides a helpful example of a mid-level theory of child well-being, demonstrating how philosophers can take relevant empirical research in a field like child well-being and build a philosophical theory out of it. The second part, ‘Tools for Science’, focuses on issues that centre on the philosophy of science, addressing questions about the objectivity of the science of well-being, well-being's measurability, and how psychometrics requires a good dose of proper philosophical reflection to be successful.

Alexandrova offers two criticisms for the study of well-being directed at both scientists and philosophers. The first criticism, aimed at scientists, is that they erroneously believe they can carry out a purely scientific study of well-being while ignoring philosophical issues, especially with regard to normative assumptions. Scientists do better by being open and explicit about certain philosophical presuppositions and offering a defence of them when possible. On Alexandrova's view the practice of science is value-laden, and the science of well-being often involves ‘mixed claims’ that combine both normative and empirical elements. Now one way that scientists might be tempted to go on is to jettison every kind of mixed claim or purify them to retain only the empirical elements. This is not how we should proceed, argues Alexandrova. One reason is that moves to purify mixed claims by removing non-empirical elements often just push the normative issues to another place (e.g. resolving disagreements among members of a community). Another reason is that over time scientists themselves often gain knowledge about values, which ‘enables them to make better normative choice qua scientists’ (p. 92). Finally, mixed claims are already ‘part and parcel of science’ (p. 105) and removing them from scientific discourse is practically unfeasible. The chief problem with retaining values in scientific practice is that doing so might endanger the objectivity of science. Alexandrova, however, believes objectivity can be preserved through the application of certain rules such as inclusive deliberation; by following these rules procedural objectivity can be secured.

The second criticism, addressed to philosophers, is that they expend far too much time and energy on the exercise of theory-building, by raising and responding to counterexamples, rather than focusing on issues that would yield much greater benefit to scientists. Here Alexandrova aims to reorient the discussion towards reflections on what she calls ‘mid-level theories’ that are connected to more concrete and contextualized issues that scientists will actually be able to make use of. Mid-level theories can also help answer the Question of Value Aptness by sharpening the focus of the scientific research, ensuring that it is properly conceptualized. Alexandrova's introduction and analyses of mid-level theories constitute one of the most innovative aspects of this book, and one that I think could play a substantial role in redirecting the attention of philosophers working on well-being. Whether or not, however, philosophers will want to seriously pursue the study of mid-level theories (e.g. child well-being, well-being among immigrants, elderly well-being, etc.) will hang on just how much good they would do for scientists as well as the extent to which philosophers will accept that building mid-level theories is a proper task for philosophers. With regard to the last point, Alexandrova makes the following remark:

As someone who has struggled to understand how we can distinguish between goods that are ‘merely’ instrumental for well-being and goods that are constitutive of well-being, I found this comment refreshing. I am inclined to agree with Alexandrova that while these are genuine distinctions, they are not as important as one might think, and at any rate, nobody has come even close to offering a sound methodology for determining the category under which a particular good falls.

The last two chapters of the book focus on well-being's measurability, making the case that focusing on mid-level theories will help make measurability a more practically implementable enterprise. Alexandrova also discusses psychometrics, raising criticisms about the way practitioners avoid theories, which can endanger the construct validity of measurements. While these are problems, they are not unresolvable, and Alexandrova is hopeful that through better psychometric practice – by paying greater attention to conceptual and theoretical issues – well-being measurements will also be improved. Again, this is where philosophers, with their background in addressing theoretical and conceptual issues, can help provide the grounding that is necessary for solid psychometric practice.

When it comes to Alexandrova's core picture of how philosophers and scientists can collaborate to advance our understanding of well-being, I am on board. One question that remains is whether or not scientists would also subscribe to this picture. (And of course not all philosophers will either.) For it is quite possible that many scientists will dismiss the need to draw on philosophical inquiries. After all, the sciences seem to keep marching on steadily without appealing to the work of philosophers. Certainly, there are mistakes made along the way, and lost time chasing rabbit holes, but the beauty of science is its ability for self-correction and its slow but steady advancements. And while I readily acknowledge all the ways in which scientific practice is value-laden, I still wonder about the extent to which philosophers – with our own extremely diverse views on just about every normative issue, and deep theoretical (and metaphysical) commitments – can provide guidance to the scientists.

Alexandrova's book breaks new grounds. My hope is that contemporary philosophers and scientists will subscribe to Alexandrova's programme. If there are enough of us – both philosophers and scientists – who are willing to carry out the kind of research Alexandrova has proposed, it may generate new projects that involve deep, interdisciplinary collaborations that can truly enrich the field of well-being.