Integrating the Philosophy and Psychology of Well-Being: An Opinionated Overview

Abstract

This paper examines the integration and unification of the philosophy and psychology of well-being. For the most part, these disciplines investigate well-being without reference to each other. In recent years, however, with the maturing of each discipline, there have been a growing number of calls to integrate the two. While such calls are welcome, what it means to integrate well-being philosophy and psychology can vary greatly depending on one’s theoretical and practical ends. The aim of this paper is to provide a novel conceptual framework for thinking about integrating well-being philosophy and psychology that systematically categorizes different kinds of integration projects. We divide existing attempts in the literature into three broad categories according to the perspective from which the integration takes place: (1) top-down meta-theoretical unification; (2) psychological integration within philosophy; and (3) philosophical integration within psychology. These categories are then broken down into various further subcategories. Our aim in providing this framework is both to facilitate the assessment and comparison of existing integration attempts and to provide a roadmap for future integration attempts. For each category, we discuss one or two representative examples of the approaches. By doing so, we hope to generate interest in the wide variety of existing integration projects, as well as to generate discussion concerning the benefits and pitfalls of different approaches.

1 Introduction

Most of us care about well-being, be it our own or that of other people. It is this common interest that underlies the wide variety of inquiry into well-being. For the most part, however, different disciplines and sub-disciplines investigate well-being without reference to each other. But once different well-being disciplines reach a suitable level of maturity, we should expect a certain level of integration and unification. Each discipline purports to investigate the same thing, after all, so it would be surprising if the findings of one approach had no bearing on the others.

This article examines the state of play regarding the integration of two major well-being disciplines: philosophy and psychology. In many ways, well-being philosophy and psychology differ in their aims and scope. Well-being philosophy is a branch of ethics that answers fundamental questions about the nature of well-being understood as a kind of value. Well-being psychology answers empirical questions about the causes, correlates, and consequences of well-being, its general levels, and so on. Nonetheless, both disciplines aim to understand the nature of well-being, broadly construed, and in recent decades well-being research has become a firmly established sub-field in both disciplines. This is especially so in psychology, where a shift in focus away from psychopathology and towards ‘positive’ aspects of human psychology has been facilitated by huge advances in measurement. Not only this, but there has also been growing governmental, institutional, and public interest in well-being (for an overview of recent trends in academic research, public discourse, and governmental policy-making relating to well-being, see World Happiness Report, Chapter 5, 2022: Rowan, 2022). Thus, the integration of the two disciplines is not merely of theoretical interest; it has the potential to offer a more unified and integrated approach to informing intervention, prevention, policy, and public understanding.

In recent years, there have been an increasing number of proposals to integrate well-being philosophy and psychology. What we see, however, is that there is no one thing that integration consists in. Rather, there are different ways of integrating well-being philosophy and psychology corresponding to different theoretical and practical ends. The central purpose of this paper is to get clear on what these are by providing a systematic categorization of different kinds of integration projects. The aim of providing such a taxonomy is twofold. First, it aims to provide a clearer and more systematic understanding of existing attempts in the literature to unify well-being philosophy and psychology. This is important because, despite the growing number of calls to integrate the two approaches (e.g., Alexandrova & Fabian, 2022), exactly what this amounts to is often not made explicit, making it difficult to compare different attempts. Second, it aims to aid future integration projects by providing a clear conceptual framework in which to develop such attempts. Because integration can mean many things, it is vital for the success of any such project that its goals and scope are properly understood.

To this end, we divide integration projects into three broad categories corresponding to the perspective from which the integration takes place. The first approach aims to unify or systematize psychological and philosophical research from an overarching meta-theoretical perspective; we call this approach top-down unification. The second approach aims to integrate psychological research into well-being philosophy; we call this psychological integration. The third approach aims to integrate philosophical research into well-being psychology; we call this philosophical integration. Each category is then broken down into further subcategories (see Table 1 for a summary). The categories and subcategories described are not mutually exclusive. It is possible for any one integration project to integrate well-being philosophy and psychology in more than one way. Moreover, there may be further categories and subcategories that we have not considered. Nonetheless, we anticipate that our taxonomy will provide a useful and novel framework that is comprehensive in relation to the integration projects we survey.

Table 1 Summary of categories

In addition to this constructive task, the paper also includes critical discussion of the research we examine along the way. To make space for such commentary, we have chosen to focus on one or two representative examples for each type of integration project rather than to attempt an exhaustive overview of all existing approaches. However, given the broad scope of the study, this commentary will necessarily be limited. We offer it not as the final word but to generate discussion in a constructive spirit. Finally, this study focuses only on Western philosophy in the analytic tradition and the hedonic and eudaimonic traditions in well-being psychology. We have chosen this focus for two reasons. First, while it would be desirable to examine other philosophical and psychological traditions, we lack the space to adequately discuss the many complex and heterogenous traditions that might be drawn on. Second, we focus on these traditions in particular because of the volume of research carried out in recent years within these fields (for example, the terms ‘subjective well-being’ and ‘psychological well-being’ and their cognates regularly top lists of keywords in scientific abstracts; see Rowan, 2022) and because they offer some of the clearest examples of the kind of integration that we are interested in (but see Lee et al., 2013, for an example of Confucian philosophy integrated into well-being psychology). While the exclusion of other traditions is a genuine limitation of the present study, we do not see any reason why our proposals cannot be fruitfully applied more broadly. We welcome such further research.¹

2 Top-Down Unification

The first type of integration project we examine is top-down unification. Top-down unification aims to unify existing psychological and philosophical research within a single comprehensive framework (see Willroth, 2023, for the importance of a unified conceptual framework). Below we examine three ways in which this might be carried out, which we will call top-down taxonomy, top-down meta-theoretical unification, and top-down methodological unification.

2.1 Top-Down Taxonomy

When mapping out any theoretical landscape, it can be useful to classify different theories within a more general taxonomy. A good taxonomy can help to compare theories with one another, see their differences and similarities, and understand the overall range of theoretical options. However, for the most part, philosophical and psychological taxonomies of well-being theories have been developed independently. In philosophy, the most common taxonomy is Parfit’s (1986) distinction between hedonist theories, desire-fulfilment theories, and objective list theories.² In psychology, the most common taxonomy is Ryan and Deci’s (2001) distinction between hedonic theories and eudaimonic theories.³ Despite their prominence, however, these taxonomies are in many ways inadequate. For instance, Parfit’s taxonomy seems to exclude Aristotelian theories of well-being (among others), and the distinction between hedonia and eudaimonia in psychology ignores important differences that cut across this distinction, such as the category of analysis (e.g., behaviours, experiences, functioning, etc.). This has led to various proposals to broaden or reconceptualize the standard taxonomies, both in philosophy (e.g., Fletcher, 2013; Haybron, 2007; Woodard, 2013) and psychology (e.g., Huta & Waterman, 2014; Lambert et al., 2015; Tov, 2018; Vittersø, 2018).

For the most part, however, such proposals remain intradisciplinary, only taxonomizing theories within philosophy or psychology. Moreover, despite various commonalities between philosophical and psychological theories of well-being, philosophical and psychological taxonomies do not map straightforwardly onto each other. For instance, whereas philosophical hedonism understands well-being entirely in terms of pleasurable and painful experiences (e.g., Crisp, 2006), ‘hedonic’ measures of well-being in psychology also encompass life satisfaction measures, which are cognitive evaluations of one’s life (e.g., Diener, 1984). If we wish to compare different philosophical and psychological theories of well-being, we might therefore hope to develop a common framework by which to categorize such theories on equal terms. This is what we call a top-down taxonomy.

A recent example of a top-down taxonomy comes from Intelisano, Krasko, and Luhman (2020), who provide a top-down taxonomy comparing philosophical and psychological well-being theories on two independent dimensions. The first dimension compares the degree of stability possessed by a theory’s well-being constructs, measured on a 5-point scale (transient = 1; stable = 5). The second dimension compares the type of psychological process, also measured on a 5-point scale (1 = purely affective; 5 = purely cognitive). To illustrate, theories of subjective well-being in psychology posit three components of well-being: positive affect, negative affect, and life satisfaction. Using their taxonomy, the authors gave positive and negative affect a rating of 2 for stability (i.e., fairly transient) and 1 for psychological process (i.e., purely affective).⁴ Life satisfaction, by contrast, was rated 4 for stability (i.e., fairly stable) and 5 for psychological process (i.e., purely cognitive). By rating other theories of well-being on the same dimensions, the taxonomy facilitates comparisons of different kinds of theories according to a common scale. For example, one can compare the authors’ ratings of positive and negative affect with the their ratings of the constructs of philosophical hedonist theories, such as quantitative hedonism (stability = 1; process = 1), qualitative hedonism (stability = 2; process = 3); and attitudinal hedonism (stability = 3; process = 3). While these dimensions are not intended to be exhaustive of the ways in which we might compare well-being theories, they nonetheless highlight two central ways in which well-being theories may differ.

A possible limitation of this taxonomy, however, is that affective and cognitive mental states do not obviously represent different ends of a single continuum. Arguably, such mental states are simply different in kind. Further, the scale leaves out a whole class of mental states that are of central importance to many well-being theories, namely conative mental states, such as desires, preferences, goals, and so on (on the distinction between cognition, affection, and conation, see Hilgard, 1980). Consequently, the authors categorize desire and preference satisfaction constructs as purely cognitive where they are more plausibly conative.

More generally, a possible limitation of top-down taxonomizing is that taxonomical differences might be more reflective of the different constraints facing each kind of inquiry, given their differing aims, than of deep theoretical differences about the nature of well-being. Thus, whereas a philosophical theory might aim to identify the constitutive elements of well-being (e.g., desire fulfilment), a psychological theory might aim to identify indicators or reliable proxies (e.g., life satisfaction) of something else too difficult to measure directly (e.g., desire fulfilment). This might lead to very different classifications, even where the underlying view of well-being is the same for both theories. Thus, even where philosophical and psychological theories can be categorized according to the same taxonomy, care must be taken in interpreting the similarities and differences that the taxonomy gives rise to.

2.2 Meta-Theoretical Unification

The shared language of well-being notwithstanding, a moment’s reflection on the subject matter of well-being philosophy and psychology might lead one to conclude that these inquiries lack a common subject matter. Philosophical theories of well-being purport to describe the nature of a particular kind of value, one identified by its place within a network of ethical or normative concerns.⁵ Psychological theories of well-being purport to describe the nature of an empirically posited psychological attribute, one identified as latent in various kinds of observable measures. So how, then, are such theories related to one another? One might answer this question from a specifically philosophical or psychological perspective (see Sects. 3.2 and 4.2 respectively). But one might also answer it from an overarching meta-theoretical perspective. In our terminology, to do this is to provide a meta-theoretical unification.

A recent example of meta-theoretical unification is Mitchell and Alexandrova’s (2021) conceptual pluralism (see also Alexandrova, 2017). According to conceptual pluralism, there is no single concept of well-being. Rather, there are many different concepts of well-being. In any discussion or inquiry, which well-being concept we employ is determined by the context. Thus, when discussing the design of educational settings in schools, the operative concept might be child well-being; when discussing resource allocation within a hospice, the operative concept might be end-of-life well-being; and so on. Perhaps there is also a global concept of well-being that concerns how well one’s life goes for one all-things-considered (think of Solon’s injunction to call no man happy until he is dead). But conceptual pluralism denies that “different concepts of well-being are merely fragments of an overarching concept” (Mitchell & Alexandrova, 2021, p. 2425). Thus, child well-being is not simply that aspect of global well-being that relates to one’s childhood; the two notions are conceptually distinct.

Insofar as conceptual pluralism offers a unified theoretical framework for well-being philosophy and psychology, it can be thought of as providing a kind of meta-theoretical unification. If there are multiple concepts of well-being, none of which has conceptual priority outside of the specific contexts in which they are used, then this provides a straightforward explanation of why the subject matter of well-being philosophy and psychology appear to differ: namely, they do differ. Because of the differing aims, scope, and limitations of different kinds of inquiry, the particular well-being concepts picked out within those inquiries will differ from each other. As Mitchell and Alexandrova note, “The construct of well-being used by a palliative care nurse to assess the well-being of his patients may hardly overlap at all with the construct of well-being used by an urban planner to assess the impact of her plans and policies on citizens’ well-being.” (2021, p.2425) However, while we agree that well-being discourse is highly context sensitive and that it is appropriate to use different constructs in different contexts, we are less confident that conceptual pluralism provides the best explanation of this.

First, it seems possible to explain the contextual phenomena that Mitchell and Alexandrova highlight without appealing to conceptual pluralism. As Fletcher (2019) argues, in different contexts we might use well-being vocabulary to talk about different aspects of well-being, and in different contexts the salient thresholds of what counts as doing well will differ. But this is compatible with the idea that these aspects and thresholds relate to a single, global concept of well-being. Second, we believe that the normative justification for any well-being concept will ultimately derive from its relation to global well-being. For instance, if our concept of workplace well-being had no relation to how well our lives go globally, is this something we should care about as well-being researchers? Third, conceptual pluralism leaves mysterious what all these different concepts of well-being have in common and why we should think of them under a unified umbrella at all. If well-being philosophy and psychology are simply studying different things, what could they have to learn from each other? A simpler, more parsimonious view is that in different contexts we are interested in different aspects of a global notion of well-being, understood as what we possess when our lives go well for us. However, the question remains for any such view of how exactly well-being philosophy and psychology are related.⁶

2.3 Methodological Unification

Philosophy aims to answer fundamental questions about the nature of well-being and its value. Typically, it proceeds from observations and reflections about our ordinary experiences, practices, and judgments about well-being to providing more systematic accounts of well-being that make sense of those experiences, practices, and judgments. By contrast, psychology aims to generate empirical evidence about general levels of and individual differences in well-being, as well as its causes, consequences, and correlates. Typically, it does this in three stages: (1) developing theories of well-being, (2) developing measures of well-being, and (3) using those measures to empirically test hypotheses about well-being. These are clearly two very different ways of investigating well-being. In the context of integrating well-being philosophy and psychology, we might therefore ask how these methodologies can be integrated. As before, this question might be answered within philosophy or psychology (see Sects. 3.1 and 4.1 respectively). But we might also provide a top-down methodological unification that seeks to provide a general methodology encompassing both disciplines.

A recent example of methodological integration comes from Prinzing (2021a), who proposes a conceptual engineering approach to the study of well-being.⁷ The basic idea behind conceptual engineering is that where our concepts fail to adequately serve our theoretical or practical ends, we should create or ‘engineer’ new concepts that better serve those ends (see, e.g., Burgess et al., 2020). Prinzing argues that well-being research is a case in point. On the one hand, philosophical inquiry leads to intractable disputes that Prinzing argues are reflective of the inconsistencies inherent in our ordinary concept of well-being (see also Bishop, 2015). On the other hand, Prinzing argues, the concepts of well-being employed in psychological inquiry, while well suited to measurement, are normatively inadequate, in that concept choice is not sufficiently guided by normative considerations (i.e., considerations about what we ought to promote in relation to well-being; we return to this issue in Sect. 4). The solution to these problems, Prinzing concludes, is for philosophers and psychologists to come together to create new concepts of well-being according to criteria derived from both disciplines. Specifically, Prinzing proposes that we create new well-being concepts that are suitably (1) normative, (2) measurable, (3) precise, and (4) mutable (relative to the context of inquiry in which those concepts are employed).⁸

We welcome Prinzing’s call for interdisciplinary collaboration. While conceptual engineering offers an interesting framework for methodological integration, however, the proposal itself remains somewhat programmatic. Moreover, we are unsure whether conceptual engineering is essential for the kind of interdisciplinary work Prinzing envisages. A simpler proposal would be that philosophers and psychologists work together to create constructs of well-being that model specific aspects of well-being (ordinarily understood) that are salient in particular contexts of inquiry—constructs, moreover, that are suitably normative, measurable, precise, and mutable. There is a sense in which this might involve creating new well-being concepts for specific theoretical or practical ends. But it is quite different to the project of conceptual engineering, which is to replace our existing concepts with new and improved ones. For if our new well-being concepts model aspects of what is denoted by our ordinary concept of well-being, they do not aim to replace our ordinary concept of well-being. Moreover, it might turn out that the tools we need already exist within our conceptual repertoire. Further, we suspect that any new well-being constructs must be suitably related to our ordinary concept of global well-being to count as suitably normative (see Sect. 2.2). However, it is unclear whether our preferred meta-theoretical underpinning differs significantly in practical terms from Prinzing’s proposal, so we do not wish to overstate the differences.

2.4 Conclusion

We have examined three distinct ways in which one might integrate well-being philosophy and psychology via top-down unification, focusing on three recent examples in the literature that implement these respectively. By aiming to integrate well-being philosophy and psychology within an overarching unified framework, top-down integration is perhaps the most ambitious type of integration project. While this potential can be seen as an advantage of this approach, this feature is also likely to make this approach the most difficult. On the one hand, the more comprehensive the approach, the greater difficulty there will be to accurately and meaningfully compare very different types of theories. On the other hand, the more programmatic the approach, the greater the difficulty to implement the unification in a fruitful and novel way. A difficulty inherent in top-down unification is thus to strike a suitable balance between these two dangers. A potential advantage, however, is that top-down integration is more readily amenable to interdisciplinary collaboration, which we believe is essential to successful integration.

3 Psychological Integration

As we will use the phrase, psychological integration refers to attempts to integrate psychological research within well-being philosophy. We examine two different kinds of psychological integration, which we will call methodological integration and theoretical integration.

3.1 Methodological Integration

The integration of psychological methodology within well-being philosophy, or more simply methodological integration, occurs when philosophers utilize the distinctive methodologies of psychology for the purpose of establishing philosophical conclusions. Perhaps the most prominent example of this in philosophy more generally is the relatively new field of experimental philosophy (see Knobe & Nichols, 2017 for an overview). Experimental philosophy seeks to employ the methods of the experimental sciences to answer traditional philosophical questions. For instance, philosophy commonly uses thought experiments to probe our intuitions about the application of a term or concept in various hypothetical situations. Where this traditionally involves an individual making such judgments from the armchair, as it were, a major strand of experimental philosophy involves testing reactions to thought experiments using random samples of lay persons in experimental settings. The idea is that such studies will give us a better idea about how people ordinarily think about the term or concept in question.

In relation to well-being, this might involve asking participants to assess how well an individual is doing in various hypothetical scenarios. A popular subject of investigation has been Nozick’s (1974) experience machine thought experiment, in which we are asked to imagine that we could plug into a virtual reality in which we subjectively experience whatever life we wish to live. While many take the experience machine as evidence that hedonism is false, since they assume that most of us would not wish to live such a life, some worry that this might be more reflective of status quo bias and other irrelevant factors like imaginative resistance (e.g., De Brigard, 2010; Weijers, 2014). This has led some researchers to test this assumption in experimental settings that attempt to control for irrelavent factors, for example by using ‘reserve’ examples in which participants are asked whether they would ‘unplug’ from the experience machine if they discovered their life so far was in fact lived inside the experience machine (De Brigard, 2010), or changing the subject of the thought experiment from the participant to a stranger (Weijers, 2014). However, while participants in these experiments are more likely to recommend plugging into the machine, it is stipulated that life inside the experience machine is more pleasurable than the real life alternative. This is a problem because even those who deny hedonism need not deny that some lives are better than others because they contain more pleasure or less pain. To use the experience machine to test hedonism, we need to imagine that the life in the machine contains the same amount of pleasure and pain than the corresponding real life (see Rowland, 2017 and Lin, 2016 for discussion).

Other studies have tested folk intuitions about theories of well-being more directly. In a recent article from Bronsteen and colleagues (2024), the authors present two studies in which sets of participants (Study 1: N = 1,253, M_age = 37.0; Study 2: N = 1,128, M_age = 37.4) were asked to rate on a 7-point scale how well a hypothetical individual’s life goes for that individual in different hypothetical scenarios (1 = not at all well; 7 = very well). Each scenario varied in levels of happiness, preference satisfaction, and objective accomplishment. The idea is that testing folk intuitions about such cases provides evidence of whether people accept some kind of hedonist, desire fulfilment, or objectivist theory of well-being. The authors found that people tend to think that happiness, preference satisfaction, and objective accomplishment all matter for well-being, thus suggesting a kind of well-being pluralism.⁹ The authors also found evidence of hedonic dominance, i.e., the belief that happiness matters more than preference satisfaction or objective accomplishment (this supports previous unpublished findings by Kneer & Haybron).

While the results of these studies only provide direct evidence about what people think about well-being, this might be taken as indirect support for well-being pluralism and hedonic dominance. However, there are some empirical issues that we believe should first be addressed. Most notably, in order to obtain accurate, reliable, and meaningful results on folk theory, it is necessary to test hypotheses on a sufficiently large and representative sample. Because of this, it is standard practice in experimental research to conduct selectivity analysis (to ensure the sample is representative) and power analysis (to ensure the sample size is large enough given the statistical module used) (for an overview see Abraham & Russell, 2008). Although the results of a power analysis (if conducted) were not reported, the complexity of statistical model (3 × 3 × 3 ANOVA indicating 27 conditions) and inclusion of numerous interaction effects and levels per condition imply that the sample size used (Study 1: N =  ~ 46 per condition) may not have had sufficient power to reliably detect effects (see MacCallum et al., 1996).¹⁰ While it is difficult to comment on the representativeness of the sample without the results of selectivity analyses (if conducted), it is worth noting that participants were recruited through Amazon’s Mechanical Turk, which previous psychological research has shown to produce participant groups that are not representative of the wider population (e.g., see Keith et al., 2017 for review and recommendations).¹¹ Future studies might therefore benefit from providing justification for sample sizes, providing power analyses to assess whether a statistical effect was possible within the statistical framework used given the data points available, and addressing issues of selectivity and representativity.

3.2 Theoretical Integration

The integration of psychological theory within well-being philosophy, or more simply theoretical integration, occurs when psychological theory is used to support or develop philosophical theories of well-being. Given the relative youth of well-being psychology, it is fair to say that psychological theories of well-being are more often influenced by philosophical theories (see Sect. 4.2). However, there has also been some productive travel in the opposite direction. Given the hegemony of the big three theories in contemporary well-being philosophy, one attraction of looking to psychological theories is that it has the promise of providing fresh perspectives on well-being. We examine two recent examples of theoretical integration, one drawing from hedonic psychology and one drawing from eudaimonic psychology.

3.2.1 Bishop’s Network Theory

An example that integrates theory from hedonic psychology is Bishop’s (2015) network theory of well-being. Bishop takes an “inclusive approach” to well-being theorizing, according to which “we must begin with the assumption that both philosophers and scientists are roughly right about well-being, and then figure out what it is they’re all roughly right about.” (2015, p.2) They go on to observe that a large part of well-being psychology involves studying the structure and dynamics of positive causal networks, understood as self-sustaining systems of positive feelings, attitudes, traits, and accomplishments. An example in psychology of this kind of network that is cited by Bishop in support of his claim about the object of inquiry of well-being psychology is Frederickson’s (2001) broaden-and-build hypothesis, according to which experiencing positive affect broadens one’s thought-action repertoire, which increases one’s physical, psychological, and social resources, which in turn promotes positive affect. Another example from psychology given by Bishop is Lyubomirsky et al.'s (2005) happiness-success feedback loop, according to which success causes happiness, which in turn causes more success. Bishop’s network theory then holds that well-being consists in such positive causal networks. Thus, according to the network theory, one does well when one’s positive feelings, attitudes, traits, and accomplishments are causally interlinked in a self-sustaining cycle.

We believe that Bishop’s theory provides one of the most interesting and illuminating attempts to unify well-being philosophy and psychology to date. That said, one might question Bishop’s argument for the network theory. For one can accept the claim that well-being psychology consists in the investigation of positive causal networks without accepting the claim that well-being consists in positive causal networks. The inclusive approach only requires that psychologists are “roughly right” about well-being, and so one need only assume that causal positive networks are in some way appropriately related to well-being (e.g., as a proxy, correlate, predictor, antecedent, etc.). This issue becomes particularly pressing if we take seriously the idea that philosophical theories of well-being are normative theories. For it is one thing to say that well-being psychology in fact studies positive causal networks and quite another to say that this is what psychologists ought to study insofar as they are concerned with well-being (Haybron, 2015 raises a similar worry). That said, these considerations only challenge Bishop’s argument for the network theory; they do not challenge the theory directly. Given that the theory is plausible and interesting in its own right, it merits further investigation.

3.2.2 Besser-Jones’ Eudaimonic Theory

An example that integrates theory from eudaimonic psychology is Besser-Jones’ (2014) theory of eudaimonic well-being. Besser-Jones aims to provide an ethical theory grounded in self-determination and self-regulation theories in psychology. Drawing heavily from the work of the psychologists Deci and Ryan (in particular Deci & Ryan, 2000 and Ryan & Deci, 2001), Besser-Jones argues that well-being partly consists in the fulfilment of certain innate psychological needs, specifically the needs for competence, relatedness, and autonomy. Because fulfilling these needs involves engaging in certain kinds of experiences, doing well consists in a kind of active functioning. Besser-Jones then builds an ethical theory of what it is to live well and virtuously in terms of an empirically informed account of what human beings are capable of doing and thus what can be reasonably expected from us. This contrasts with more traditional eudaimonistic philosophical theories that begin with armchair reflection about the fully virtuous agent, who is then posited as an ideal to which we should aspire. The hope is that an empirically informed account will be better suited for providing practical advice on how to live well.

From a philosophical perspective, Besser-Jones’ theory offers a rich, novel, and interesting account of the nature of well-being. However, it is less clear whether and how the empirical theory Bessor-Jones builds on supports their theory. A common issue in psychology is that there is often a conflation between components and predictors of well-being—that is, between what well-being is and what causes well-being.¹² This is especially prominent in the eudaimonic tradition, where eudaimonia is sometimes identified as constitutive of well-being, and at other times identified as a pathway to well-being (see Henderson & Knight, 2012). It is vital not to conflate these notions, especially in the context of constructing a philosophical theory, as they merit very different kinds of investigation: whereas identifying the components of well-being is a theoretical task, identifying predictors of well-being is an empirical task. A philosophical theory is therefore only concerned with identifying the former.

With this in mind, it is interesting to note that much of the psychological research appealed to by Bessor-Jones in support of their theory seems to conceptualize needs fulfilment as a pathway to well-being rather than a constituent. One might see this as an issue because Bessor-Jones (2014, p. 22) takes this research “to see needs satisfaction as constitutive of” rather than as “the cause” of well-being.¹³ For instance, Ryan and Deci describe needs fulfilment as a pathway to well-being. In an overview of their research, they describe needs fulfilment as “facilitating … personal well-being” (2000, p. 68), having an “impact … on health and well-being” (2000, p. 69), as something that “conduces toward health and well-being” (2000, p. 74), and so on. This is also reflected in the empirical evidence they cite in support of their theory, including one study which found that “variations in the fulfillment of each of the three needs … independently predicted variability in daily well-being” (2000, p. 76). Moreover, they sum up their discussion by observing that the studies they discuss “support the view that basic psychological needs are determinative with regard to optimal experience and well-being in daily life.” (2000, p. 76) It is worth noting, however, that many of these studies used methodological approaches that can only provide partial and indirect support for this claim (e.g., cross-sectional designs used to test causal pathways: Kasser & Ryan, 1993, 1999).¹⁴ Moreover, this body of evidence also seems to conflate needs fulfilment as a pathway to and/or constituent of well-being.¹⁵ Further, Ryan and Deci frequently define well-being in terms not typically used in well-being psychology (referred to as ‘well-being indicators’; see Ryan & Deci, 2000, p. 75).¹⁶

Thus, if self-determination theory conceptualizes needs fulfilment as a pathway to well-being, offering empirical support for this claim, then we might worry whether this research supports Bessor-Jones’ theory, which conceptualizes needs fulfilment as a component of well-being. Moreover, while we lack the space here to undertake a comprehensive literature review of self-determination theory, we believe the above worries warrant further investigation into its conceptual and empirical underpinnings. However, as with our discussion of the network theory of well-being, these considerations challenge only Besser-Jones’ argument for the needs fulfilment theory, not the theory itself. Thus, we still believe that the needs fulfilment theory is an interesting proposal in its own right that merits further investigation. Philosophers sympathetic to the eudaimonic approach might also stand to benefit from exploring the prospects of a philosophical theory based on the other dominant eudaimonic theory in psychology, Ryff’s theory of psychological well-being (for more on which, see Sect. 4.2.2).

3.3 Conclusion

There are many advantages to integrating well-being psychology within well-being philosophy. Applying psychological methods to philosophical questions can create new knowledge for philosophers that can play an important role in assessing what ordinary people actually think about well-being. Further, psychological theory provides rich and new perspectives for philosophical theorizing about well-being. Given their training, philosophers should be especially well-placed to interpret and develop theories implied by or already found in well-being psychology. While many well-being constructs in psychology find their equivalent in well-being philosophy, philosophers rarely engage in the kind of in-depth exploration of psychological theories that we have seen above.¹⁷ However, the approach also brings with it its own difficulties. In relation to integrating methodology, experimental philosophical research should be sure to employ the necessary methodological rigour without sacrificing the conceptual nuance required for philosophical argumentation. In relation to integrating theory, philosophical research should make sure to take a critical eye towards the conceptual and empirical underpinnings of psychological theory. So while there is much to be gained for philosophy from psychological integration, it also offers distinctive challenges.

4 Philosophical Integration

We now move on to our final category, philosophical integration. As we will use the phrase, philosophical integration occurs when well-being psychology aims to incorporate aspects of philosophical theorizing. We examine two different kinds of integration, roughly corresponding to the two different kinds of psychological integration discussed above, which we will call methodological integration and theoretical integration.

4.1 Methodological Integration

Methodological integration in this sense occurs when the methodologies of philosophy are incorporated into well-being psychology. In some ways, this category is less well-defined than the other categories. This is because it is notoriously hard to state exactly what philosophical methodology consists in. For many of the hallmarks of philosophical inquiry, such as systematic reasoning at an abstract level, are not unique to philosophy but present in any systematic inquiry, including psychology. For these reasons, we focus on just one aspect of methodological integration relating to the idea that well-being research is essentially value-laden or normative. We focus on this aspect because questions of value and normativity are traditionally seen as within the purview of philosophy. Thus, if questions about well-being are fundamentally normative questions, as philosophers commonly maintain (e.g., Darwall, 2002; Fletcher, 2021; Railton, 1989), well-being psychologists will need to be sensitive to the ways in which philosophers address such questions.¹⁸ As Alexandrova and Fabian (2022, p. 8) observe in a recent review article, “As wellbeing research grows interdisciplinary, the main contribution of philosophy is an awareness of and sophistication around the value judgments involved in defining wellbeing.”

An interesting proposal for how psychologists might incorporate such philosophical methodology is Alexandrova and Haybron’s (2016) discussion of construct validity in psychometrics. As mentioned above (Sect. 2.3), a major component of well-being psychology is measurement development, in which proposed measures of well-being are subjected to various kinds of tests to establish their empirical validity. This process, known as construct validation, is required because many of the constructs posited by psychological theory, such as positive and negative affect, are not directly observable. Instead, psychologists measure such constructs via directly observable variables, such as self-report questionnaires, in which the posited variables are assumed to be ‘latent’. Given the gap this opens up between theory and measurement, the purpose of construct validation is to ensure that we are measuring what we think we are measuring. This process involves numerous steps, most often beginning with exploratory and confirmatory factor analysis, which are used to determine how many constructs a set of questionnaire items measure by estimating the degree of variance they share. Once it is established that an item is measuring one latent construct, researchers will next test for the convergent, discriminant, and predictive validity of that item, which estimate whether it correlates with related variables, does not correlate with unrelated variables, and predicts related outcomes respectively. When a measure is validated according to these statistical tests, we say that the measure is valid.

Without denying the importance of construct validation, Alexandrova and Haybron argue that its current practice is insufficient to determine whether well-being measures are genuinely valid. As they see it, construct validation is problematically theory avoidant, in that it sacrifices “valid theoretical knowledge for statistics for no good reason” (2016, p. 1103). They provide two examples of this in relation to well-being research. First, in relation to convergent and discriminant validity, they argue that different researchers may disagree about which variables we should expect to correlate with well-being. For instance, suppose some well-being measure fails to correlate with material prosperity. Depending on one’s prior views about the significance of material prosperity for well-being, one might interpret this finding either as supporting the measure’s discriminant validity or undermining its convergent validity. Second, they argue that reliance on exploratory factor analysis leads us to ignore important sources of evidence when selecting measures. As an example, they discuss the positive and negative affect schedule (PANAS, Watson et al., 1988), a widely used questionnaire that measures 20 discrete positive and negative emotions arrived at by using factor analysis on a long list of English mood terms. Alexandrova and Haybron argue that this methodology fails to capture how some of these emotions are plausibly more central to well-being than others and how other important emotions are not included on the list, such as anxiety, stress, and peace of mind.

In both cases, Alexandrova and Haybron diagnose the problem as one of theory avoidance. They propose that to avoid these problems, construct validation should additionally test for normative validity, where this involves testing the measure against normative assumptions relating to the construct being measured. To a certain extent, it might seem unfair to criticize construct validation as atheoretical, since theory development of the construct under study is a stage of inquiry prior to construct validation (see Sect. 2.3).¹⁹ Moreover, once we observe that theory development is a prior stage of inquiry, then insofar as our choice of theory is normatively justified, we might expect our measures to already possess normative validity. That said, given the gap that the pressures of construct validation create between one’s constructs and measures, testing for the normative validity of one’s measures would arguably be of additional benefit. Further, granting that construct theorizing is simply a different stage of inquiry, it is nonetheless the case that psychologists (and social scientists more broadly) frequently skip this critical step. ²⁰ So even if the central role of normative considerations is in theory development rather than measurement development, they might still have a role to play in the latter, and the more general call for avoidance of theory avoidance is welcome.

4.2 Theoretical Integration

Theoretical integration in this sense occurs when philosophical theory is incorporated within well-being psychology. To a certain extent, philosophical influence within well-being psychology has been present from the outset. This is for the simple reason that while philosophical reflection on well-being has existed for thousands of years, well-being psychology is a relatively recent enterprise. So it is only natural that psychology would look to philosophy for insight, especially insofar as philosophy has influenced and codified ordinary societal thought about well-being. This section presents a brief overview of the philosophical underpinnings of the two main schools of thought in well-being psychology, as well as examining a more recent attempt to integrate contemporary philosophical theory into psychological research.

4.2.1 Hedonics

The hedonic tradition in well-being psychology largely focuses on so-called subjective well-being, where this encompasses an individual’s subjective evaluation of (aspects of) their life, as well as their overall balance of positive and negative affective states (for an overview, see Diener et al., 2018). It is often claimed that the hedonic tradition developed atheorethically (e.g., Alexandrova & Fabian, 2022, p. 13). While there is some truth in this, it is important to understand the broader intellectual tradition within which hedonic psychology is situated. Its lineage can be traced back to the British utilitarians, such as Bentham and Mill, who argued that well-being consists in the presence of pleasurable experiences and the absence of painful experiences, and that public policy should be tailored accordingly. While many economists in the early twentieth century accepted this view, they wanted to find more empirically tractable measures of well-being, which led to the use of economic indicators as proxies for well-being (e.g., Pigou, 1932). Dissatisfaction with this approach in the second half of the twentieth century and the rise of psychometrics led to the use of self-assessment questionnaires to ask people to directly report their subjective assessments of how things are going (e.g., Cantril, 1965; Bradburn, 1969; Andrews & Withey, 1976; Campbell et al., 1972; for an early overview of such measures, see Wilson, 1967). Given this (admittedly thumbnail) history, we submit that hedonic psychology is most charitably underpinned by a theory of well-being according to which well-being consists in the balance one’s positive and negative subjective states. As Campbell (1976, p. 118) sum it up, “the quality of life lies in the experience of life.” (For more on this history, see Campbell, 1976 and Sumner, 1996; for a more detailed and nuanced history of subjective well-being measures, see Angner, 2011).

It seems overwhelmingly plausible that well-being is at least in some way related to one’s positive and negative subjective states. However, this admittedly vague idea needs to be made more precise, and it is precisely here that hedonic psychology could benefit from a closer engagement with its philosophical underpinnings. For the most part, hedonic psychology has precisified this idea in response to the demands and constraints of developing empirically adequate measures. However, this has left certain fundamental questions unaddressed. For instance, subjective well-being, the central construct of contemporary hedonic psychology, is composed of life satisfaction, positive affect, and negative affect. While each component can be described as a kind of positive or negative subjective state, it is not obvious they form a unified, natural kind. After all, positive and negative affect are, unsurprisingly, affective states, whereas life satisfaction is typically understood as a cognitive judgment. This matters because the kinds of rationale one might offer for one component might not apply to the others. After all, hedonists like Bentham and Mill would not countenance life satisfaction within their theories of well-being since life satisfaction judgments are not pleasurable experiences.

Interestingly, some theorists offer a unified rationale for subjective well-being that justifies positive and negative affect on non-hedonistic grounds—namely, that positive and negative affective states are themselves kinds of evaluations of one’s life, and subjective well-being more generally consists in an individual’s evaluation of their life (e.g., Diener et al., 1998). Philosophically, this is an interesting suggestion, one that is not typically given by defenders of philosophical hedonism.²¹ Moreover, it relies on a substantive position in the philosophy of mind that many would see as controversial.²² By contrast, others working in the hedonic tradition provide a more traditionally hedonistic rationale for subjective well-being. For instance, Kahneman and Krueger (2006) claim that life satisfaction assessments are retrospective assessments of temporally aggregated positive and negative experiences (for a similar view of overall happiness reports, see Bradburn, 1969). While this provides a straightforward rationale for subjective well-being as a unified construct, it seems doubtful that life satisfaction measures aggregate transitory well-being as the authors suggest. For instance, even if I know that my day-to-day work life is generally unpleasant, I may still rate my work-related life satisfaction as high for other reasons, say because of the importance I take the work to have.²³

It might be thought that such debates, while interesting, are purely academic and make little difference to the practice of well-being psychology. However, this would be a mistake. One’s choice of measures must be given adequate theoretical rationale, and different rationales can lead to different measures. For instance, if what matters for well-being is positive and negative experiences, then arguably one should jettison life satisfaction measures in favour of more reliable proxies of temporally aggregated positive and negative experiences. Further, if what matters for well-being is subjective evaluations of one’s life, then in the absence of a robust defence of the idea that affective states are evaluations of one’s life, positive and negative affect measures should arguably be jettisoned. This reemphasises that well-being psychology cannot avoid difficult philosophical questions about the nature of the psychological states and processes implicated in well-being psychology (see also Nussbaum, 2008).²⁴

Perhaps subjective well-being can be justified disjunctively, giving different rationales for affective and life satisfaction measures. However, once we allow for a plurality of justifications of well-being constructs, this invites the question of why we should treat subjective well-being as having the kind of distinctive importance that hedonic psychology assumes it to have. To adopt this approach is not to deny that subjective well-being matters. Rather, it is to accept that it is one thing that matters among others. Indeed, this kind of pluralism seems to have been endorsed by early proponents of the hedonic tradition; for instance, Bradburn (1969, p. 224) colourfully describes affective measures as but one species of tree in the forest of psychological well-being. However, adopting a pluralist approach does question the usefulness of bringing affective and life satisfaction measures together under a single overarching construct rather than treating them as separate.²⁵ And quite apart from this, some philosophers question whether affective and life satisfaction measures are appropriate measures of well-being in the first place (see, e.g., Nussbaum, 2008; Haybron, 2008).

4.2.2 Eudaimonics

The history of the eudaimonic tradition in well-being psychology is both newer and older. It is newer in that much of the contemporary eudaimonic tradition came about in part as a reaction to the perceived shortcomings of the hedonic tradition (e.g., Ryff, 1989a). However, it is older in that it explicitly draws from Aristotle’s eudaimonistic ethics. There is less overall agreement about the precise constructs and measures involved in this approach. As we have already examined self-determination theory (Sect. 3.2.2), we will focus here on the other main strand of contemporary eudaimonic psychology, Ryff’s theory of psychological well-being (e.g., Ryff & Singer, 2008; Ryff, 1989a, 2013). Ryff’s overarching construct of psychological well-being has six components: self-acceptance, positive relations with others, autonomy, environmental mastery, purpose in life, and personal growth. The choice of these components draws heavily from humanistic psychology throughout the twentieth century (Ryff, 1989b), as well as a qualitative study interviewing middle and older-aged adults (Ryff, 1989c). The development of the psychological well-being scale thereafter underwent the standard statistical practices involved in construct development and validity (i.e., scale construction followed by scale validation via convergent and divergent validity and factor analysis; Ryff, 1989a). However, it is also explicitly based on Aristotle’s views of well-being, in that it aims to capture the idea that well-being consists in “striving toward excellence based on one’s unique potential” (Ryff & Singer, 2008), with an emphasis on functioning well over feeling good.

As with the hedonic tradition, we believe that the eudaimonic tradition could benefit from a closer engagement with its philosophical underpinnings. For instance, as Keyes and Annas (2009, p. 197) note, the particular interpretation of Aristotle upon which the eudaimonic tradition is premised is “outdated”, “eccentric”, and does not engage with the bulk of contemporary scholarship on Aristotle’s ethics (for an overview of the latter, see Kraut, 2022). Ryff’s (1989a) seminal paper on psychological well-being endorses Waterman’s definition of eudaimonia as “the feelings accompanying behavior in the direction of, and consistent with, one’s true potential” (Waterman, 1984: 16). Waterman’s understanding of eudaimonia is in turn derived from Norton’s (1976) so-called ethics of individualism, according to which the good life is one in which one actualizes one’s true self, or daimon. While this kind of description of Aristotle’s eudaimonism is common in the psychological literature (e.g., Ryan & Deci, 2001; Ryff & Singer, 2008; Waterman, 2008; Henderson & Knight, 2012; Tov, 2018), it is practically absent from the philosophical literature. Thus, there is an emphasis in eudaimonic theories on notions of personal growth, personal expressiveness, realizing one’s potential, authentic living, and so on, that are not at all central or present in philosophical Aristotelian views of well-being. Insofar as Aristotle is invoked to provide the philosophical underpinnings of eudaimonic theories, it is therefore questionable whether such invocation is entirely successful.

A closer reading of Aristotle might suggest new ways of developing well-being constructs and measures in the eudaimonic tradition. For instance, Aristotle’s central idea in the Nichomachean Ethics is that the good life for a human being is one of activity in accordance with excellence.²⁶ Since developing one’s capacities for excellence is a lifelong task, this is clearly related to the idea of self-realization or personal growth found in eudaimonic psychology. However, whereas these ideas are inward-looking towards the self, Aristotle’s conception is outward-looking towards the activity itself and the external standards by which it is judged to be excellent. Thus, for example, if we imagine someone who dedicates their life to teaching, the quality of their life is to be judged (in part) not from their sense of personal development with regard to teaching, but from whether their teaching was genuinely excellent. Thinking about well-being in this way might therefore lead us to incorporate more objective measures of eudaimonic well-being. Alternatively, it might lead us to develop subjective measures that measure individuals’ perceptions of how their activities fare against more objective standards of excellence.²⁷

4.2.3 Project Fulfilment

A more recent example of integrating philosophical theory within psychological research comes from Bedford-Peterson et al.'s (2019) study of success in personal projects. The importance of personal projects is supported from a number of different philosophical perspectives. For instance, many objectivist views hold that success in one’s personal projects is a component of well-being because of the value of objective achievements (e.g., Bradford, 2015). Moreover, many subjectivist views hold that the fulfilment of desires or values related to one’s personal projects has a special or central role in relation to one’s well-being (e.g., Dorsey, 2021). Given this widespread philosophical interest, the authors aim to bring a central but neglected dimension of well-being into focus within empirical study. They present a longitudinal study (N = 196; M_age = 18.70; range: 18–25 years; 75% female) measuring personal project success, finding current (but not past) project success to be associated with both hedonic and eudaimonic well-being measures. However, it is worth noting that measures most directly associated with hedonic well-being, positive and negative affect, displayed only inconsistent associations with personal project success across analyses, indicating only tentative support for the idea that personal projects are related to hedonic well-being.

The authors take an ecumenical approach that aims to reflect widespread agreement of the importance of personal projects for well-being despite lack of agreement about the explanation for their importance. Because of this, the study is often ambiguous regarding whether personal project success is a pathway to or constituent of well-being. For instance, success is explicitly modelled as a predictor (i.e., pathway) of subjective well-being in their second set of analyses (structural equation modelling). By contrast, their first set of analyses uses a correlational analysis to establish association (amount of variance shared) between success in personal projects and each indicator of well-being, which leaves it ambiguous as to whether success in personal projects is conceptualized as a pathway to or constituent of well-being. Further, given that the authors remain non-committal regarding exactly which philosophical rationale for personal project success they accept, it is unclear to what extent the study successfully integrates philosophical theory into psychological research, especially since the different philosophical rationales offered are not consistent. (It is also worth observing, as the authors do, that the study of project success is not itself alien to well-being psychology: see, e.g., Emmons & Diener, 1986; McGregor & Little, 1998; Sheldon & Elliot, 1999). Moreover, as we have seen above, theoretical rationale is not irrelevant for one’s choice of measures. For instance, if personal projects are valuable only insofar as they are an instance of something else of value (e.g., desire fulfilment or objective achievements), then we may be more justified in measuring the broader category rather than a narrow subset of it (i.e., personal project success).

4.3 Conclusion

Well-being psychology is to varying degrees already implicitly or explicitly guided by philosophy. Indeed, given the nature of the subject matter, we believe that a certain amount of philosophical theorizing is unavoidable. However, it is also desirable. Much of psychological investigation into well-being is driven by the constraints of measurement. Because these constraints are by their nature very different to those governing theory, this naturally creates a gap between what is measured and what one’s prior theory says well-being is. Psychological research must therefore not lose sight of the theory that motivates its measures in the first place if we are to have confidence that our measures genuinely measure well-being and not something else. Given that a certain amount of philosophizing is unavoidable in theories of well-being—whether due to the normativity of well-being or due to questions about the nature of the psychological states and processes implicated in theories of well-being—we therefore believe that psychologists would benefit from a more detailed engagement with the philosophy that underlies their theoretical and empirical decisions. However, in order for such integration to be successful, it is important for psychology to properly understand the philosophical rationales behind different approaches and to use these rationales in a consistent and well-motivated way.²⁸

5 Concluding Remarks

We began our investigation with the assumption that whatever their differences, all well-being researchers share a common concern, a concern, moreover, shared by the general public. This is the concern that things go well for ourselves, for others we know and care about, and for society more generally. Ultimately, it is this shared concern that underlies well-being philosophy and psychology. While well-being philosophy and psychology are by no means completed sciences, both disciplines have reached a level of maturity at which it is both possible and desirable to begin to provide more integrated understandings of well-being.

Our central aim in this paper was to provide clarity on the various ways in which one might go about this task. We did this by providing a systematic categorization of the three main types of integration projects, examining one or two representative examples for each type. These categories are (1) top-down unification: projects that provide an overarching unification of well-being philosophy and psychology; (2) psychological integration: projects that integrate psychological methods and theory into well-being philosophy; and (3) philosophical integration: projects that integrate philosophical methods and theory into well-being psychology. Delineating between different types allowed us to provide a clearer picture of the benefits and difficulties of existing attempts at integration, ranging from the methodological to the conceptual. We summarize such difficulties and benefits, as well as the outlook of each approach below (see also Table 1).

One of the main challenges underlying the first category, top-down unification, is the difficulty in providing an approach that is sufficiently sensitive to the reasons philosophers and psychologists have for defining or operationalizing well-being. These reasons will often be disparate, owing to each discipline’s differing aims and constraints (e.g., measurement constraints in psychology leading to different classifications of well-being constructs than in philosophy). Nonetheless, projects within this category have strong potential to spearhead interdisciplinary collaboration on a more ambitious scale. Indeed, many of the projects discussed above provide new and interesting ways to think about interdisciplinary collaboration, including those proposing new methodologies to compare existing well-being constructs across discipline (e.g., Intelisano et al., 2020), those providing theories accounting for the differences between well-being constructs in each discipline (e.g., conceptual pluralism: Mitchell & Alexandrova, 2021), and those proposing entirely new concepts based on the strengths of each discipline (e.g., conceptual engineering: Prinzing, 2021a).

One of the main challenges underlying the second category, integrating psychological theory and methods into philosophy, is ensuring that appropriate methodological standards of rigour in designing measures, surveys, experiments, etc., are maintained without compromising the philosophical rationale of the concepts and thought experiments therein. Of note, however, is that the kind of data generated by such research, while interesting, is ultimately limited in what it can show us about well-being, since it only tells us what people think about well-being. On the other hand, we believe that incorporating psychological theory into well-being philosophy shows the most promise, since such theory opens up interesting new possibilities for philosophical theorizing (e.g., Bishop, 2015; Bessor-Jones, 2014). A central difficulty for such an approach is to articulate precisely how psychological theory offers support for philosophical views. Nonetheless, even in the absence of such an account, the mere fact that such theory offers new perspectives for philosophers is itself of value.

One of the main challenges in the third category, integrating philosophical theory and methods into psychology, relating to integrating philosophical methodology into well-being psychology is to display a sufficient sensitivity to the normativity of well-being. If well-being is a normative notion, then choices about constructs and measures are in part value-laden. But given that questions of value and normativity are primarily within the purview of philosophy, psychologists will need to be sufficiently attuned to the appropriate standards of rigour for articulating and defending normative claims. Projects within this strand, such as Alexandrova and Haybron’s (2016) appeal for normativity validity within psychometrics, represent key building blocks towards overcoming this difficulty. Another major difficulty for this category relating to integrating philosophical theory into well-being psychology is to be sufficiently sensitive to the complexities of such theories and the implications that different philosophical choices make to the rationales for one’s measures (e.g., in relation to the nature of the psychological states and processes psychological theory appeals to). However, we believe that this is also a key strength of this approach, since it can offer new approaches to measurement and the possibility of coherent theoretical rationales for the proliferation of disparate measures used in empirical well-being research.

One solution that may overcome some of the key challenges underlying each category is to conduct integration projects as part of an interdisciplinary team of both philosophers and psychologists. Given the sheer scale of implementing integration (it requires the knowledge and skills characteristic to both philosophy and psychology) and the disparate aims and restraints of each discipline, interdisciplinary teams seem best suited to conduct such projects. Indeed, we see the potential for such interdisciplinary collaboration as one of the most attractive aspects of the integration of well-being philosophy and psychology, especially as it is this that is most likely to spur future research agendas in interdisciplinary well-being research.

By providing a novel framework for conceptualizing different kinds of integration projects and by highlighting some of the opportunities and caveats of adopting each approach, we hope that our framework can provide a guide for future integration projects. However, it must be noted that the research examined here has been necessarily selective. We welcome future application of our framework to other work within and beyond the traditions we have focused on. Moreover, our critical suggestions have been necessarily preliminary. We welcome further discussion of the points we have raised.

Finally, a more general lesson of the present study is the importance of intellectual modesty. Success for all types of integration project depends on a proper understanding of what is being integrated. However, given their differences in training, philosophers and psychologists are not always in the best position to understand each other’s work. This highlights the importance of proper attention being paid to the details of the research one wishes to integrate, as well as to the different aims and constraints inherent in each approach. It also highlights the desirability of interdisciplinary collaboration and training in the relevant methodologies. In other words, researchers have their work cut out for them. But the well-being of interdisciplinary research depends on it.