Fred Feldman is easily the most prominent contemporary defender of hedonism. The proposition that the good life is the pleasant life was eloquently defended, for example, in his 2004 work Pleasure and the Good Life. In his most recent book, What is This Thing Called Happiness?, Feldman bridges the gap between philosophy and science. The systematic scientific study of happiness, satisfaction and other positive or desirable mental states goes back almost a century, to the 1920s and 1930s, when empirically minded psychologists began studying systematically the determinants and distribution of happiness and the like. Yet, the empirical happiness literature was until recently largely ignored by philosophers. The first philosopher to take it seriously, to my knowledge, was Nicholas Rescher in 1972. The topic reappeared in the philosophical literature in the 1990s, as L. W. Sumner developed his account of well-being as life satisfaction in a manner that appears to have been inspired by the empirical literature, and again in the 2000s, when a number of philosophers, apparently independently, turned to this literature in order to examine how it can inform, and be informed by, moral philosophy and philosophy of science. Now, Feldman joins the conversation, with a book about ‘happiness, well-being, and interactions between psychological and philosophical research on happiness’ (p. v).

What is This Thing Called Happiness? is a solid contribution to the literature. It deserves to be widely read not just by philosophers, but by anyone with an interest in empirical happiness research or in its public policy implications. In particular, the increasing number of psychologists, economists, sociologists, epidemiologists and others doing empirical happiness research could benefit hugely from reading this work.

There are at least three important reasons to pick up a copy of this book. First, it contains a valuable analysis of the philosophical foundations of happiness research. Thus, chapter 1 reviews some of the measures that have been used in empirical studies as well as a few basic empirical results that they have generated; chapter 2 contains an examination of the account of happiness implicit in Daniel Kahneman's work; and chapter 13 discusses Richard Layard's suggestion that empirical data establish that happiness is ‘real’. Exploring the philosophical foundations of happiness studies is hard work. Social and behavioural scientists’ writings on happiness are often terribly unclear, and not only do different authors disagree with each other, but some authors appear unable to agree with themselves. In spite of the challenges, Feldman does an excellent job: his account is wonderfully clear and impeccably fair. The account is far from complete, however. There are many fascinating authors who would have deserved a fuller treatment. Thus, Ed Diener, Richard E. Easterlin and Martin E. P. Seligman, towering figures in the literature, are mentioned only in passing or ignored altogether. Moreover, throughout the book, Feldman spends a lot of time discussing measures of satisfaction rather than happiness. (The discussion of Kahneman's work constitutes an exception.) In the 1970s, psychologists came to think of happiness and satisfaction as separate constructs, and they have since developed an impressive range of measures specifically of happiness. It is not clear why Feldman so often focuses on measures of satisfaction, given his interest in happiness.

Second, Feldman's book contains a useful restatement of his own accounts of happiness and well-being, as well as the arguments in their favour, spelled out in light of more recent contributions to the literature, including Dan Haybron's work on life satisfaction. Feldman's account hinges on a distinction between two kinds of happiness. A person's sensory pleasure at a time t reflects the degree to which she experiences a particular kind of feeling or sensation at t. A person's attitudinal pleasure at a time t, by contrast, reflects the degree to which she takes pleasure in things at time t. In Feldman's view, the concepts of happiness and well-being can be fully explained by reference to the concept of attitudinal, but not sensory, pleasure. The formulation and defence of Feldman's hedonism is clear and concise, and should be easily accessible to non-philosophers as well. The part dedicated to exploring his accounts of happiness and well-being is the longest of the book, but because these views constitute familiar ground to readers of this journal, I will not discuss them in any detail here.

In this context, Feldman could have used the scientific literature to greater advantage. In discussing the implications of his account, Feldman couples his philosophical theses with various descriptive claims. Only rarely are these claims defended on the basis of scientific evidence. In his discussion of whether a person lacking in freedom and opportunity can be happy, for example, Feldman invites us to consider a story about dominated housewife Bertha, who has been socialized in such a way as to be unable to recognize that her life is demeaning and dehumanizing. Feldman believes such stories to be ‘psychologically implausible’ (p. 197), and goes on to write: ‘It is reasonable to suppose that if she had taken advantage of [the freedom to choose her style of life, etc.], she would have taken pleasure in a much richer variety of interesting things’ (p. 200). Just a few paragraphs later, Feldman talks about ‘the fact that on my view girls (and everyone else) would be a lot happier and [a] lot better off if they are raised to value freedom, creativity, and respect’ (p. 201, my italics). Whatever the exact thesis expressed in these remarks, Feldman is making claims about the determinants and distribution of happiness. Given an account of happiness, these are empirical claims, and consequently it would have been appropriate to discuss whether they are consistent with the best available evidence. While existing scientific data might not completely settle the issue, surely some such evidence would have been better than no such evidence. The point is related to a theme that resurfaces by the end of the book. There, Feldman associates with ‘science worship’ the notion that ‘philosophers had better pay more attention to the work of their colleagues in psychology or economics, lest they embarrass themselves by being ignorant of important findings that bear directly on their philosophical work’ (p. 253; cf. p. 269). Yet, as the example in this paragraph suggests, philosophical argument sometimes cannot help but proceed from empirical premises; such premises must be supported by empirical evidence; and it is appropriate for philosophers to support such premises with the best available scientific evidence.

Third, Feldman's book contains an interesting discussion of philosophical issues associated with the effort to build a science of happiness. Chapter 12 actually presents a novel measure of happiness, designed better to represent happiness as Feldman understands it; chapter 13 discusses purported metaphysical implications of happiness research, including whether happiness can be understood to be a natural kind; and chapter 14 sums the argument up. This is in many ways the most original and interesting part of the book. The questions addressed in this part are fascinating, and deserve far more attention from philosophers – and not just from moral philosophers but from philosophers of science as well. Consider Feldman's happiness measure, which is offered as an improvement over various measures of satisfaction. Feldman offers a battery of questions about (a) what the respondent has been thinking about of late, and (b) how pleased or displeased the respondent has been when thinking about each topic; on the basis of answers to such questions, Feldman argues, it is possible to construct an aggregate measure of attitudinal happiness. In addition, he points to a few considerations that can be offered for or against the proposed measure. The fact that Feldman's measure is explicitly designed to reflect a carefully crafted conception of happiness makes it quite different from the measures proposed by psychologists and economists, who find it easier to agree on how to measure happiness than how to define it.

Though interesting, this part of the book could be expanded considerably. For example, it would have been interesting to learn more about Feldman's views about existing measures of happiness, as opposed to measures of satisfaction. One of the most prominent measures of happiness, already in use for more than half a century, is based on the following question: ‘Taking things all together, how would you say things are these days – would you say you're very happy, pretty happy, or not too happy these days?’ If the prompt ‘[taking] things all together’ serves to trigger the memory of whatever ‘things’ the respondent has been thinking about ‘these days’, the measure might be a reasonably good proxy for attitudinal happiness; at the very least, it should be superior to existing measures of satisfaction. It is unfortunate that Feldman does not discuss the strengths and weaknesses of measures like these. Similarly, it would have been interesting to know what Feldman thinks about existing efforts to show that measures of happiness represent that which they purport to represent. Using techniques borrowed from psychometrics, students of happiness and satisfaction have gone to great lengths to establish – successfully or not – that their measures are reliable and valid. In addition to identifying a few considerations that can be offered for or against a given measure, it would have been relevant to discuss in greater detail the theory and practice of those who actually attempt to establish the reliability and validity of various measures – or for that matter, the writings of the philosophers of science who have already covered some of this ground. Again, it is not at all a bad idea to pay more attention to the work of colleagues in psychology or economics.

At any rate, in spite of some sections that could have been developed further, What is This Thing Called Happiness? is well worth reading. Perhaps above all, it illustrates the value of bridging the gap between science and philosophy in an area like happiness studies, where philosophers, psychologists, economists and others have intersecting interests, and where a more integrated approach can yield insights that are both fascinating and important.