# Economic Modeling of 'Axiological Rationality': a Tedious Challenge

Daniel Serra, Adda Benslimane

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# Economic Modeling of 'Axiological Rationality': a Tedious Challenge

Daniel Serra
&
Adda Benslimane

<figure><img src="image_4.png" /></figure>

CEE-M Working Paper 2025-06
Economic Modeling of ‘Axiological Rationality’: a Tedious
Challenge

Mars 2025

Daniel Serra* and Adda Benslimane**

*Key words:* Rational behavior / Morality / Axiological rationality / Kantian equilibrium / Moral preferences / Social preferences / multiple-preference models / Hierarchical-preference models

Daniel Serra, Professor Emeritus in Economics, University of Montpellier, CEE-M UMR
Univ Montpellier, CNRS, INRAE, Institut Agro

Adda Benslimane, Senior Lecturer in Economics, CORHIS, University Paul Valéry Montpellier 3
*Abstract* If we are trying to reconcile morality and rational behavior in economics, one worthy approach is to postulate that individuals are ‘rational in value’ (or ‘axiological rational’), as defined by Weber/Boudon. In many circumstances, people choose an action because they think it’s the ‘right thing’ to do without focusing exclusively on its consequences. The aim of this article is to identify in the recent history of economic ideas which approaches seem best suited to modeling axiological rationality. Three modeling modes have been selected, and their strengths and weaknesses are presented and discussed from this perspective. Some economists assume that an agent’s rational calculus takes into account an additional ethical constraint (‘constraints-based approach’). For others, morality intervenes directly in the agent’s preference system (‘preference-based approach’). In this line of research yet two approaches must be distinguished: ‘social preferences models’ assume that people have other-regarding preferences while ‘multi-preferences models’ contrast moral preferences to more material ones with the aim to construct a utility function that would reflect a compromise. A final approach can be seen as an attempt to reconcile conceptions of morality as both constraint and preference (‘hybrid’ approach) by proposing ‘hierarchical-preferences’ models, in which moral values are no longer included in the utility function but are used to filter out immoral preferences. We argue that, although each of these approaches has certain advantages in its own right, multi-preference models seem to be the most appropriate way for modeling axiological rationality.

**Résumé** Si l'on tente de réconcilier moralité et rationalité du comportement en économie, une approche digne d'intérêt consiste à postuler que les individus sont « rationnels en valeur » (ou « axiologiquement rationnels »), selon la définition de Weber/Boudon. Dans de nombreuses circonstances, les personnes choisissent une action parce qu'elles pensent que c'est la « bonne chose » à faire, sans se préoccuper exclusivement de ses conséquences. L'objectif de cet article est d'identifier dans l'histoire récente des idées économiques les approches qui semblent les mieux adaptées à la modélisation de la rationalité axiologique. Trois modes de modélisation sont retenus, dont nous présentons et discutons les forces et les faiblesses dans cette perspective. Certains économistes supposent que le calcul rationnel d'un agent prend en compte une contrainte éthique supplémentaire (« la moralité comme contrainte »). Pour d'autres, la moralité intervient directement dans le système de préférences de l'agent (« la moralité comme préférence »). Dans cette ligne de recherche, deux approches doivent toutefois être distinguées : les modèles à « préférences sociales » supposent que les personnes prennent en compte le sort des autres dans leurs préférences, tandis que les modèles à « préférences multiples » opposent leurs « préférences morales » à leurs préférences plus matérielles dans le but de construire une fonction d'utilité qui refléterait un certain compromis. Une dernière approche peut être considérée comme une tentative de réconciliation des conceptions de la moralité comme contrainte et comme préférence (approche « hybride ») en proposant des modèles à « préférences hiérarchiques », dans lesquels les valeurs morales ne sont plus incluses dans la fonction d'utilité mais sont utilisées pour filtrer les préférences immorales. Nous prétendons que, bien que chacune de ces approches présente certains avantages en soi, les modèles à « préférences multiples » semblent être le moyen le mieux adapté à la modélisation de la rationalité axiologique.
# 1. INTRODUCTION

The importance of ethical issues in everyday life is indisputable. Economists themselves are likely to be concerned when they seek to explain a variety of observed behaviors not predicted by standard theory such that ‘ethical’ consumption, participation in the financing of public goods, emergence of cooperation in social dilemma, tipping or donations to charities, participation in elections, etc. It may therefore be desirable for economists to endow their *homo oeconomicus* with some moral values.

On the other hand, in economics, the principle of rationality invites us looking to agents themselves for explaining reasons for their behavior. And the most precise definition of rationality is that individuals act by adapting their means to their ends; what is commonly termed ‘instrumental’ rationality. However, does it make sense apply rationality in the field of values? And if so, must we inevitably envisage an exclusively ‘instrumental’ rationality? For instance, cannot we choose to act with honesty or integrity without necessarily reducing this to a devious intention to increase one’s income, or being treated as thoughtless or irrational? Answering this question in the affirmative means to admit people display a form of ‘axiological’ rationality.

It was Max Weber [1922] who introduced the concept of 'rationality in value', a notion later expanded upon and refined by sociologist Raymond Boudon under the term 'axiological rationality' (Boudon [1995], [1999], [2003], [2007], [2009]. Axiological rationality follows a fundamentally different logic from instrumental rationality (which Weber called 'rationality in finality'): it is not 'consequentialist'.<fnref n="1" /> The motive for action becomes the significant *reason* for behavior, without giving primary consideration to its consequences. There may be physical, biological, psychological and sociological causes of human behavior. But studying these causes alone cannot shed light on the meaning that individual attach to them. In order to provide an 'explanatory' understanding of an action, it is necessary to interpret the meaning given to it by its author.<fnref n="2" />

In substance, a person is considered to be *axiologically rational* if she/he performs an action because she/he has good reasons to believe that it is the ‘right thing’ to do, without necessarily worrying about its consequences. In an economic choice model, an axiologically rational

<footnote n="1">¹ Consequentialism, as its name suggests, is simply the view that normative properties depend only on consequences.</footnote>

<footnote n="2">² The distinction between ‘reasons’ and ‘causes’ is crucial here: reasons motivate, explain and justify actions, while causes determine behaviors that may be thoughtless.</footnote>
behavior “reveals” preferences that are *non-outcome-based*, i.e. preferences that cannot be expressed in terms of monetary payoffs alone.

This paper seeks to identify which economic approaches, emerging in recent history of economic ideas, are most suitable for modeling axiological rationality. To this end, three modeling frameworks are examined and criticized for their strengths and weakness.<fnref n="3" /> First, some economists posit that moral behavior arises from an additional constraint in the agent's rational calculus ('constraints-based approach'), echoing Kantian philosophy, where morality is defined by adherence to a 'universalist' norm (section 2). Second, others argued that morality is embedded directly within the agent's preference system ('preference-based approach').<fnref n="4" /> In this line of research, yet, two approaches must be distinguished. Some authors draws from the works of David Hume (Hume [1740]) and Adam Smith (Smith [1759]), emphasizing the roles of emotions in people's behavior; they proposed to accept that people have *social preferences*, in that their utility function depends not just on their payoffs, but also on the others' payoffs (other-regarding preferences) (section 3). Another trend in research attributes a special characterization to *moral preferences*: certain moral concerns are explicitly implied in 'multi-preferences' models in which authors contrast moral preferences with more material preferences, trying to construct a utility function that would reflect a compromise (section 4). A third approach can be seen as an attempt to reconcile conceptions of morality both as constraint and preference ('hybrid' approach). In 'hierarchical-preferences' models, that embody that approach, values are no longer included in the utility function but are used to filter out immoral preferences; there is a 'moral view' that should be considered as a 'preference over preferences' (section 5).

## 2. MODELING MORALITY AS A CONSTRAINT: KANT EQUILIBRIUM

It is essentially because of their interpretation of Kant's 'categorical imperative' (Kant [1785], [1788]) that economists have been led to represent moral principles in the form of constraints. But the 'prescriptivism' of a philosopher like Richard Hare also leads to a vision of morality as a constraint. For Hare (1981), morality is seen as an imperative that limits and guides the choice

<footnote n="3">³ Much of the work done by economists on ethical issues has so far been carried out within the framework of Welfare economics. We consider this field to be outside the scope of our paper insofar as this branch of economics deals mainly with *aggregate* issues and focused on the *definition* of collective norms, with the aim of informing public policy.</footnote>

<footnote n="4">⁴ This dual 'constraint-preference' conceptual framework is common among economists. But it also refers to two different ways of perceiving the sources of axiology in moral epistemology (i.e., the discipline that asks the question: how do we know what is moral?) depending on whether one is a 'cognitivist' or not. The cognitivist sees morality as a set of propositions that can be shown to be 'true', which can therefore only be imposed on her/him, and in which she/he can only believe. This brings us back to the notion of constraint. The non-cognitivist (or positivist), on the other hand, refuses to attribute the terms 'true or false' to moral judgments, which are seen as the expression of desires. This leads to the notion of preference (Livet [2002]).</footnote>
of human actions. Here, we will only consider the first economic model proposed by Jean-Jacques Laffont from this perspective (Laffont [1975]) insofar as models developed subsequently by other researchers may be subject to similar limits (Sugden [1984], [1991]; Bordignon [1990]; Bilodeau and Gravel [2004], in particular).<fnref n="5" /> There is today a voluminous literature around ‘Kant equilibrium’ which, in a similar vein, studies endogenous (self and other-regarding) cooperation in a non-cooperative game-theoretical framework. After presenting Laffont’s seminal model (2.1), we turn to a critical discussion of this constraint-based approach (2.2).

## 2.1. Laffont's Seminal Model: Macroeconomic and Kantian Constraints

Laffont [1975] notes that theories that seek to explain cooperative behavior beyond what is prescribed by selfish motivations alone are in fact only valid for small groups of individuals, thanks to ‘solution’ concepts forged by cooperative game theory; they are too complex and information-intensive for large social groups. In his view, all economic action takes place within a moral framework specific to the market sphere. All commercial exchange is based on respect for contracts and the property of others. But he also observes that more and more economic interactions fall outside this sphere, in particular due to the presence of negative externalities. So what kind of morality can serve as a framework for these new interactions? In a way, it is a question of finding an alternative model of cooperative behavior that goes against the maximization of self-interest alone, while preserving the agent’s rationality.

To illustrate his point, the author takes the example of a large number of anonymous people who have the choice, on a large homogeneous beach, between throwing their own few beer can on the beach (which saves effort on their part, but inconveniences others) or taking it to a dustbin (which requires some effort on their part, but protects others from pollution). Basically, we are faced with a kind of ‘prisoner’s dilemma’, since if everyone leaves her beer can on the beach, everyone’s usefulness will be reduced. If this attitude is adopted, it may mean that: either no one anticipated that the aggregate consequences of her/his behavior would prove directly harmful, or each individual imagines that she/he is the only one to adopt this behavior.

How can cooperative behavior emerge in this kind of problem? Laffont's aim is to show that awareness of the group's interests through adoption of ‘Kantian’ behavior can contribute to this. Each individual thinks that others will act in the same way as she/he does. If she/he decides to leave the beer can on the beach, and everyone else does the same, the beach will quickly become impassable. It is therefore not in her/his interest to adopt this selfish behavior

<footnote n="5">⁵ In fact, this reference to the Kantian categorical imperative in economics is an old one; it had already been mentioned by Paul Samuelson in the 1950s (Samuelson [1954]).</footnote>
(provided, of course, that she/he intends to return to the beach...). In the decision-making model, each individual is thus faced with a new "macroeconomic constraint". Before choosing a particular action as the result of "maximizing one's utility under her/his budget constraint", each individual will have to undergo a mental experiment consisting in generalizing her/his choice to the rest of the population. And if the result is undesirable, then the action in question is not the 'right' solution to the problem. Generalization of an action's choice is therefore a constraint that weighs on agent's decisions. It is a question of linking our action to that of others through a mental exercise that takes us back to our own choice when it is acceptable from a Kantian point of view.

Faced with these situations of negative externalities in consumption, the traditional solution of economists is to advocate introducing a tax. However, such a policy would entail considerable costs in terms of implementation, monitoring and collection, so that Paretian optimality is of secondary importance. The alternative proposed by Laffont, on the other hand, involves only a minimal cost, since for encouraging agents to adopt a Kantian behavior, it would only take a few efforts to inform them of the existence of macroeconomic constraints.

The author also develops a dynamic extension of this reasoning, based on an overlapping-generation model. The problem here is that each individual imagines the future state of a situation in terms of her/his own actions alone, rather than through the aggregation of everyone else's actions. Here again, taking macroeconomic effects into account through the adoption of Kantian behavior should be able to change this view. If individuals behave selfishly, the only way to guard against undesirable future states is to make everyone pay insurance. This insurance can be seen as a tax to finance the treatment of undesirable effects. For example, it could be a tax automatically levied on any walker approaching the seashore, as a fine levied on people caught defacing it would be too costly to implement. Here, what can be seen as a macroeconomic constraint involves protecting oneself against certain future conditions by having to opt for the costly solution of individual insurance. It would be better to choose responsible, far-sighted behavior, representing a kind of collective insurance against these undesirable states. In short, it would simply be a matter of making everyone aware of the undesirable effects of the negative externalities of their consumption on others and on the environment in general.

It would seem that by adopting this way of thinking about the relationship between rational economic behavior and moral, we are led to look for a kind of 'fixed point' in people's beliefs. This is precisely what was later suggested and formalized in a game-theoretical setting by John Roemer who coined the name of 'Kant equilibrium' to describe this state in which, by
adopting a ‘universalist’ ethic norm, self-interested players are cooperating in non-cooperative
settings (Roemer [1996], chap. 6, [2010], [2019]). In a Kantian equilibrium, each player is self-
regarding and maximizes her/his own payoff akin to Nash players. Unlike Nash players,
however, a Kantian player does not treat others’ actions as parametrically given but assumes
that other players act as she/he does.<fnref n="6" />

## 2.2. Axiological Rationality and Kantian Economics: A Critical Discussion

What are we to make of this way of modeling axiological rationality in economics? Does it
comply with the definition laid down? One can legitimately remain somewhat skeptical.
Wolfelsperger ([1999], [2001]), in particular, has expressed strong reservations about this
‘Kantianism of the economists’ from the authentic Kantian point of view: ‘Human action takes
on a moral value only when it is guided not by interest but by duty, i.e., by pure respect for the
moral law as such. In this case, what is supposed to motivate individuals to follow this law is
precisely that, thanks to it, they will achieve the Pareto-optimal state they desire. But from a
Kantian point of view, it is contradictory to make morality as means to an end’ (Wolfelsperger,
[1999], p. 883) (our translation). So this approach to integrate moral aspects into the modeling
of individual choice doesn’t seem very convincing. Not only axiological rationality is completely
reduced to instrumental rationality, but the legitimacy of the term ‘Kantian’ to describe this
behavior attributed to individuals also is questionable.<fnref n="7" />

In that model, according to Wolfelsperger, moral attitudes would be merely a means of
achieving efficiency at the lowest possible cost; for each individual, morality would be reduced
to taking account of her/his interests in a broad, long-term perspective, without neglecting
social interactions. Agents would choose an action on the basis of its foreseeable
consequences, not its intrinsic value. In a way, the Kantian categorical imperative ('do this
because you must') would be transformed into a pragmatic or hypothetical imperative ('do this
to get that'). As we know, according to Kant, moral obligation must above all be unconditional.
'Morality begins where strategic instrumental rationalization ends' (our translation) (Livet

<footnote n="6">⁶ Expressed another way: Nash player reasons as followed: ‘given what others are playing, what is the best strategy for me?’ while a Kantian player thinks as followed: ‘What is the single strategy I would most like all of us to play?’ This recent economic literature also involves the concept of ‘Berge equilibrium’ (Berge [1957]), recently rediscovered in game theory (see Colman et al. [2011]). In Berge equilibrium, each player treats other players’ strategies parametrically — which is identical to the counterfactual of Nash players — but the difference is that each player — unlike Nash players — is purely altruistic and maximizes other player’s payoff (see e.g. Unvere, Donduran, and Barokas [2023]). Several variants have been studied in the literature, e.g. ‘mental equilibrium’ (Winter et al. [2017]) or ‘rational altruistic equilibrium’ (Tobias [2023]). What all these models have in common is that they describe altruism or cooperation as the result of a calculation. Individuals take others’ well-being into consideration because they may well ultimately find it in their best interests to do. In fact, it’s reminiscent of Becker’s rational altruism (Becker [1974], [1976], [1996]).</footnote>

<footnote n="7">⁷ It is true that Roemer acknowledges that “the term is used for its suggestive meaning and do not wish to imply that there is a deeper Kantian justification of [his] proposal (Roemer [2019], p. 220, fn 7).</footnote>
[1999], p. 226). But in this framework, moral obligation is in fact reduced to a simple calculation of costs and benefits, a sign of a strong epistemological departure from an essentially ‘deontological’ orientation. There is no room in this construction for any form of axiological rationality since moral rules are not the object of choice; they do not in any way express a purpose that would be pursued for its own sake. A similar critique was made by Mark White (White [2009]), for whom Kant’s philosophy favors the cooperative solution without making it necessary.

More generally, we must question the legitimacy of this formal translation of morality as a ‘chosen’ constraint into economic models. Of course, this represents a particular advantage on the formal level by simply limiting the range of choices available to the individual. By the way, this undoubtedly explains why economists are so keen on this type of modeling. But considering morality as a mere constraint, in the same way as economic or technological constraints, seems far from our current ethical intuitions. Especially since assuming that we are all capable of imposing moral rules on ourselves may seem rather counter-intuitive when we refer to the notion of constraint as defined in economic theory. For an economist, a constraint is clearly unwanted.

Despite the criticisms mentioned above, however, some researchers have developed a line of defense for this way of integrating axiological rationality into choice modelling in economics (see Picavet and Gravel [2000]; Picavet [2011]). These authors claim that there is compatibility between the ‘Kantian’ representation of an axiologically rational behavior and optimization of the individual objective.<fnref n="8" /> From this point of view, a presentation of individual goal maximization under the constraint of similarity in the actions chosen by some and others presents an advantage for the description of individual rational choices in terms of theoretical unity. ‘It is only a particular *interpretation* of this model of choice, in terms of an exclusively self-centered search for the means to achieve the best results (according to personal criteria), that can give impression of reducing morality to an instrumental dimension. In reality, the essential point is impersonality, and personal criteria intervene only as representatives of a class of criteria that are indistinguishable in terms of the conclusions they deliver. It is chosen in preference to the others only for epistemological reasons of unity in the theoretical modeling of decisions (typically, the defense of the general model of optimizing individual’ (Picavet [2011], p.216) (*our translation*). For these authors, then, using a model based on optimization under a constraint of similarity of actions chosen by some and others does not imply assimilation of morality to an

<footnote n="8">⁸ However, this is only valid in a situation that verifies symmetry properties in the positions of one and other. This important condition had already been mentioned by Laffont [1975] and even by Samuelson [1953].</footnote>
instrumental search for self-interest. In fact, we would simply come up against the limits set by
the very framework of rational choice theory.

If the idea of rationalizing morality as an 'internalized' chosen constraint is abandoned, it
seems logical to model it as a preference. In this line of though, yet, two distinct approaches
have been explored. The most widespread of these among economists has been to relating
moral values to emotions felt by agents in various contexts of interactive behavioral decisions.
We are talking here about behavioral economics modeling of 'social preferences'.

3. MODELING MORALITY AS A PREFERENCE: ‘SOCIAL PREFERENCES’ MODELS

Social preferences models must be divided into two classes which need to be distinguished:
distributional models (31) and intentional models (32).

3.1. *Distributional Models of ‘Social Preferences’*

It is well known that contemporary behavioral economics seeks to explore the economic consequences of some traits of human psychology: bounded rationality, bounded will-power, bounded self-interest (Thaler [2015]). These three major limitations of human psychology form the basis of what Richard Thaler called ‘quasi-rationality’ (Thaler [1994]). They are at the heart of behavioral economics: cognitive limits (i.e., the existence of bounded rationality)<fnref n="9" />, the weaknesses of individual will-power (i.e., a problem of self-control)<fnref n="10" /> and the social character of preferences (i.e., the existence of ‘other regarding preference’) (Serra [2022], p. 84).

It is this latter aspect of human psychology that is likely to be invoked when addressing the
issue of axiological rationality. The aim of social preference models is to account for pro-social
or cooperative behavior often observed in real life and in a large number of economic
experiments. In these models illustrating the social nature of preferences, access to individual'
moral value is thought to be provided by the varied social emotions experienced by individuals
in a wide range of circumstances. We therefore suggest interpreting these models as a way of
modeling axiological rationality by endorsing the thesis put forward by some moral
philosophers, that our moral values were 'revealed' by our emotions (Gibbard, 1990; Livet,
2002).<fnref n="11" />

<footnote n="9">⁹ Human cognitive capacity is not unlimited, especially in terms of memory and the ability to evaluate available information; hence the frequent use of heuristics by people in decision making.</footnote>

<footnote n="10">¹⁰ People make decisions that they know are bad for them, but which they are unable to avoid. This implies, in particular, time-inconsistencies in decisions making.</footnote>

<footnote n="11">¹¹ Emotions 'reveal our values, in a sense not unlike that in which our choices reveal our preferences. We do not need to choose to have preferences, but it is in choosing that we reveal our preferences to ourselves. We can make value judgments without experiencing emotions, but it is by experiencing emotions that we reveal our values to ourselves' (Livet [2002], p. 177-178, *our translation*). Remark this thesis contrasts with Boudon's view that values *inspire* emotions, rather than the other way</footnote>
Many of these behavioral models maintain the optimizing and selfish behavior hypotheses of standard theory, but at the same time they incorporate an additional norm of behavior in the form of an internalized constraint that no longer appears as a limitation on the space of choices (as in the Kantian economics framework mentioned in section 2) but rather as an exogenous preference. This includes for instance a 'taste for giving' (Andreoni [1990], [1995]), a 'preference for honesty' (Andreoni, Erard, and Feinstein, 1998) or a 'preference for fairness' (Bolton and Ockenfeld [2000], Fehr and Schmidt [1999]).<fnref n="12" />

For Andreoni ([1990], [1995]), an individual experiences a positive affect — named a 'warm glow effect' — when, for example, she/he decides to contribute to the funding of a public good. This 'taste for giving' is then included in her/his utility function in the same way as the search for self-interest, giving rise to a certain degree of arbitration. But only the act of giving is positively valued, without being associated with any particular moral motivation. On the other hand, in 'distributional models' developed in behavioral economic from seminal models of Bolton and Ockenfels [2000]) and Fehr and Smith [1999], agents are supposed to be motivated in their choice by a fairness concern; they show a 'preference for fairness' which, however, takes on different forms depending on the model.

In Bolton & Ockenfels' model, called ERC (Equity, Reciprocity, Competition), the focus is on the relative monetary gains of agents: when making their decisions, individuals are assumed to care about not only the absolute amount of money they receive but also their relative standing compared to others. More precisely, according to these authors, fairness judgements are based on a kind of mental reference outcome, which itself is the product of a complex social comparison process. Behavior of agent i is assumed to be dictated by maximizing the expected value of her 'motivation function':

$$v_i = v_i(y_i, c_i),$$

where $y_i$ is the monetary gain of agent i, and $c_i = y_i / \sum y_i$, the agent's share of the final distribution. Notice this function has properties that reflect the authors' choice of egalitarian sharing as the social reference point in their basic model. But they rightly recognize that one of

<footnote>round (Boudon [1994]), just as it differs fundamentally from Ayer's 'emotivism', according to which values only reflect emotions of the person issuing them (Ayer [1936]). In the other hand, we should point out that an author like John Elster, in his influential work about rationality, does not subscribe to the concept of axiological rationality, but he suggests taking emotions to explain some behaviors. In his view, the influence of emotions encourages individuals to devalue the consequences of their actions. They can hinder or even prevent rational thinking. Generally, unless emotions are very intense, an individual is motivated by both reason and emotion; this is what he calls 'mixed motivation' (Elster [1999]). For him, this is the hallmark of a non-consequentialist behavior, as distinct from axiological rational behavior in the sense of Boudon. This is also the case with Robert Frank (Frank [1988]), for whom emotions play an important role in decision-making, even if they appear irrational.</footnote>

<footnote n="12">¹² Behavioral economics models of this kind also include work on different kinds of altruism (Andreoni and Miller [1996], [2002]), altruism and spitefulness (Levine [1998]), envy (Kirchsteiger [1994]), or guilt (Battigalli and Dufwenberg [2007]).</footnote>
the weaknesses of their model lies in identifying the 'appropriate' group to define the social norm of reference when considering a situation with more than two individuals (Bolton and Ockenfels [2008]). The ERC model postulates a certain heterogeneity among individuals, each of whom is characterized by threshold parameters that reflect her/his trade-off between acceptance of the social norm and the pursuit of strict self-interest.<fnref n="13" /> In a nutshell, in that model, cooperation is explained by the interaction between player heterogeneity and the scale of gains, in particular the maximum potential payoffs resulting from cooperation.<fnref n="14" />

The Fehr-Schmidt model defends an idea similar to that underlying the ERC model, namely, to integrate into individuals' motivation a concern about final distribution of gains. But the embodiment of this idea is significantly different, since these authors postulate that some individuals are motivated by 'inequity aversion': they are ready to sacrifice a fraction more or less important of their personal gains for lowering inequities. Yet this is a 'self-centered' aversion, in the sense that individuals are concerned only with fairness of their own material gain relative to others' gains. As in the ERC model, agents determine themselves in relation to a social reference point, which is assimilated to an egalitarian distribution: inequity aversion can be approximated by inequality aversion.

More precisely, two assumptions characterize the model: (i) The population includes both selfish subjects: subjects who dislike being worse off in material terms than other players in the experiment, and subjects who dislike being better off; (ii) Generally, individuals suffer more from inequality that is to their disadvantage than from advantageous inequality. In the particular two-player model the utility function of agent i is:

$$u_i = x_i - a_i / |x_j - x_i| - b_i / |x_i - x_j| \quad j \neq i$$

with parameters $a_i$ and $b_i$ such that $b_i \le a_i$, $b_i \ge 0$ and $b_i \le 1$, and given that the monetary gains $x_i$, $x_j$ are common knowledge. The second term of the expression measures the psychological loss the individual suffers when her/his own gain is lower than that of the other ($x_i < x_j$). Parameter $a_i$ is interpreted as a coefficient of envy (or even anger or indignation) since it measures the extent to which the individual suffers from the fact that the other obtains more than she/he does. The third term also measures the psychological loss the individual suffers, but this time when her/his own gain is greater than that of the other ($x_j < x_i$). Parameter $b_i$ is thus interpreted as a coefficient of guilt (or even shame or embarrassment). Condition $b_i \le a_i$ expresses the idea that a player suffers more from inequality that is to her/his disadvantage, i.e., envy is stronger than guilt. Condition $b_i \ge 0$ rules out the existence of subjects who like to

<footnote n="13">¹³ Formally, this is a game with incomplete information, and the 'ERC equilibrium' is defined in the model as a perfect Bayesian equilibrium, which is resolved with respect to players' motivation functions and in which their thresholds are known only to them.</footnote>

<footnote n="14">¹⁴ A first version of this model was proposed in Bolton [1991].</footnote>
be better off than others. Condition $b_i \le 1$ means that it is very implausible that a subject's utility loss is very strong when the inequality is to her/his advantage.

Like the ERC model, the Fehr-Schmidt model can explain both cooperative and non-cooperative behavior in a lot of non-cooperative games. In the presence of inequality-averse people, 'cooperative' (i.e., fair) as well as 'non-cooperative' (i.e., competitive) behavioral patterns can be explained in a coherent framework. The main insight of this study is that 'the heterogeneity of preferences interacts in important ways with the economic environment' (Fehr & Schmidt, 1999, p. 818). More precisely, it is proved that the economic environment determines the preference type that is decisive for the prevailing behavior in equilibrium. In the end, the main advantage of the Fehr-Schmidt model is that it reveals the conditions under which the existence of inequality-averse players influences the equilibrium of a game.

As for the ERC model, however, a set of questions is related to the choice of the 'reference' group and the 'reference' outcome. For instance, there may well be interactive situations in which some agents have a salient position which makes them natural reference agents. Further, it is likely that the social framework and the institutional environment in which interactions take place are significant (Montet and Serra [2003], p. 458).

Distributional models have enjoyed some popularity among economists, as they claim to rationalize pro-social behavior without abandoning the hypothesis of utility maximization and the consequentialist point of view. However, they do give rise to a number of reservations: for example, the somewhat ad hoc approach of explaining the existence of *equitable* behavior by an *aversion to inequity* is questionable. Moreover, these models account for a trade-off between a material preference and a moral preference by means of *exogenous* monetary parameters alone, without assuming any actual interaction between individuals (Wolfelsperger [2001]; White [2004]).

It is true that authors of these distributional models, as we have said, interpret their model by referring to some social emotions felt by individuals during comparisons: envy (or anger or indignation) when the comparison is unfavorable, guilt (or shame, or simply embarrassment) when it is favorable. But is not that just an artifice? The model, as it is constructed, only accounts for one dimension of the emotional process through the utility function: its valence, i.e., the pleasant or unpleasant nature of the sensation associated with decision's consequences (Petit [2012]).

We have to conclude that neither models associated with the 'taste for giving' nor distributional models really mention motivations or intentions specific to the theory of emotions. In truth, emotions result from internalization by individuals of rules of behavior. If we ignore
them, we underestimate the fact that these rules are more endogenous preferences than exogenous constraints imposed on the individual (Petit [2012]). This is precisely what is proposed by another family of social preference models named ‘intentional models’.

## 3.2. Intentional Models of Social Preferences

In distributional models, agents are supposed directly attached to final distributions; only the outcome matters. In contrast, in ‘intentional models’, individuals are supposed to care more about the reasons that lead to the final distributions: intentions are taken into account, in the same way as agents’ expectations or the context of the decision. More precisely, in these intentional models, individuals are mainly motivated by ‘reciprocity’ concerns<fnref n="15" />. Incidentally, this suggests that the appropriate framework for studying this phenomenon involves postulating that agents make their choices sequentially and not simultaneously.<fnref n="16" />

In his seminal model, Rabin [1993] summed this idea up perfectly: ‘People tend to be generous to those who are themselves generous, and hostile to those who are themselves hostile’ (p. 1281). He developed a ‘fairness equilibrium’ that includes these stylized facts. ‘Positive reciprocity’ is defined as a kind response to an action driven by fair intentions, while ‘negative reciprocity’ is defined as a hostile response to an action driven by unfair intentions.

To formalize fairness, he modified conventional game theory by allowing payoffs to be a function of players’ beliefs as well as of their actions, and he builds a ‘psychological game’ in which player i’s subjective expected utility $U_i$ depends both to the strategy chosen by i ($a_i$) player j’s beliefs about what strategy player j is choosing ($b_j$), and player j’s beliefs about what player j’s believes player i’s strategy is ($c_i$).<fnref n="17" /> Rabin assumes that utility inputs are provided in two forms: material-based and fairness-dependent. This corresponds to a total utility:

$$U_i(a_i, b_j, c_i) = u_i(a_i, b_j) + f_j^*(b_j, c_i)[1 + f_i(a_i, b_j)]$$

where $u_i$ is the utility from material benefits, while the utility derived from the fairness of the outcome is represented by the product $f_j^*$ and $[1+f_j]$, given that $f_i$ is a first ‘kindness function’ representing how kind i (hereafter named ‘she’) is actually being to j (hereafter named ‘he’) and $f_j^*$ is a second ‘kindness function’ representing how kind i thinks j is being to her. The definition of the first kindness function involves a ‘fair’ payment defined somewhat arbitrarily as the average between the maximum and minimum payments that i gives to j, the latter providing a

<footnote n="15">¹⁵ Reciprocity seems to be a principle of conditional cooperation universally accepted in all cultures; as such, it is part of the ‘moral sense’ common to all human beings (Wilson [1993]). It is even considered to be present in certain animal species (see Schweinfurth and Cale [2019], in particular).</footnote>

<footnote n="16">¹⁶ In formal terms, we are dealing with sequential games rather than normal-form games.</footnote>

<footnote n="17">¹⁷ The concept of ‘psychological game theory’ was introduced by Geanakoplos, Pearce and Stacchetti [1989] and extended by Battigalli and Dufwenberg [2009]. For an overview, see Battigalli and Dufwenberg [2022].</footnote>
crude reference point against which to measure how generous player *i* is being to player *j*. Intuitively, if *i* thinks *j* is going to act fairly toward her, she is more likely to act fairly in return. When both act fairly, both derive positive 'psychological utility' from the exchange in addition to any material utility. By contrast, if *i* thinks *j* is going to act unfairly toward her, her incentive to act unfairly in return will be increased. In other words, acting fairly toward a partner who is unfair reduced the actor's materially based and psychologically based utility. And a player also receives psychological utility by acting selfishly towards one that acts selfishly towards her.

Rabin defines a 'fairness' equilibrium as a Nash equilibrium of the 'psychological game' and such that an additional property holds: players' beliefs must be in conformity with players' actual behavior. Generally the equilibrium where both agents act fairly is preferred. It can be proved that when the material payoffs are small, fairness motivations outweigh self-interest, but when they become large, players' behavior is dominated by material self-interest. There is in fact a strong asymmetry in this model with a bias toward negative reciprocity. However, Nelson (2001) proved that if the relationship between material and fairness inputs is generalized, by not specifying how they interact while providing utility, fairness becomes a normal good as stakes move from high to very high.<fnref n="18" />

To sum up, the main contribution of Rabin's model is to have insisted on the *conditional nature of* decision making, repeatedly highlighted by experimental studies. While Rabin's model is the most innovative of this early literature on social preferences, subsequent types of model have also been proposed that give emotions a more central place, such as taking into account the role of social approval (Holländer [1990]), social pressure exerted by peers (Kandel and Lazear [1992]) or agents' expectations (Rotemberg [2008]; Charness and Dufwenberg [2006]).<fnref n="19" />

In the other hand, other interesting approaches have tried to merge intention-based reciprocity and distributional equity. For instance, in Falk and Fishbacher [2006], 'kindness' is measured in terms of inequity aversion. Charness and Rabin (2002) also proposed a hybrid model in which agents care about their own payoffs, and about a weighted average of the lowest payoff anybody receives (a kind of 'Rawlsian' or quasi-maximin component, by reference to the theory of justice developed by Rawls) and the sum of all payoffs (a kind of

<footnote n="18">¹⁸ A combination of experimental results (ultimatum game) and of charitable-giving data (natural dictator game played outside of the laboratory) show how in this case Rabin’s value function is consistent with empirical evidence (Montet and Serra [2003], chap. 8).</footnote>

<footnote n="19">¹⁹ There is an abundance of experimental literature which, following the first experiment undertaken by Sally Blount (Blount, 1995), establishes the role of conditional preferences, intentions or reciprocity in a wide range of archetypal economic sittings such as public-good games, trust games and bargaining games See the surveys by Rabin [1998], Sobel [2005], Rotemberg [2006] as well as the monographs by Winter [2014] and Serra [2017].</footnote>
‘utilitarian’ component). Their model has a hidden aversion to inequality through the emphasis
on the lowest payoff; so, it incorporates a specific form of altruism. But, in addition, agents are
assumed to care also about the others’ actions.

What about these social preference models in relation to our topic? Do they offer a more
satisfactory way of formalizing axiological rationality than the constraint-based approach
previously put forward? We have to admit that by taking into account the role of emotions in
decision-making — a result now widely documented by research in decision neuroscience and
neuroeconomics<sup>20</sup> — behavioral models explain many empirical facts of social life or
experimental and empirical regularities that classic monetary maximization models are unable
to account for. However, even if these models incorporate a description of human psychology
that can make sense of a lot of observed cooperative and pro-social behaviors, they remain
essentially *outcome-based*, i.e., people are supposed to care only about the consequences of
their decisions. This explains in particular why some empirical or experimental facts cannot be
taken into account in these models of social preferences.

4. MODELING MORALITY AS A PREFERENCE: ‘MULTIPLE PREFERENCES’ MODELS

Today, the microeconomic literature also includes another trend of researcher taking a
closer look at the multiplicity of individual motivations. More specifically, we have a large
number of ‘multiple preferences’ models designed to take formal account of the existence of
*moral preferences*. These models assign special characteristics to moral preferences as
opposed to more material ones, by asking whether a compromise can be reached.

We will proceed in roughly chronological order, and give just a few examples from a now
abundant literature.<fnref n="21" />

Etzioni (1986) proposes to distinguish between ‘pleasure’ and ‘duty’, the former relating to
self-interested choices, the latter to respect for some values and norms. According to Etzioni,
we associate our selfish preferences with pleasure-seeking, whereas duty often requires us to
perform tasks we find unpleasant. But how do you calculate a final choice based on these two
components? If we simply add them together, we are back to standard choice theory, and

<footnote n="20">20 One of the first unanimously recognized lessons of decision neuroscience and neuroeconomics for economists is to have confirmed in objective terms that emotions play a central role in decision-making at the neural level, whether they are presented as indispensable to instrumentally ‘rational’ decision-making, whether they are expected to work closely with control and evaluation processes, or whether they appear to act in competition with cognitive processing of the decision. For an introduction to neuroeconomics and an overview of neuroeconomic experiments on social decision, see Serra (2016). A wide range of results from this new interdisciplinary field of research can be found in Glimcher et al. (2009), Glimcher and Fehr (2014) and Serra [2021].</footnote>

<footnote n="21">²¹ See in particular Capraro, Halpern, and Perc [2024]'s recent survey for models that try to explain human behavior in social interactions described by normal-form games.</footnote>
'duty' then enjoys no special properties. If this is not desirable, we need to explain how two presumably incommensurable parameters can lead to a unique choice (Isaac [1997]).

Kuran's model (Kuran [1998]) illustrates another attempt to separate moral values from material interests. It takes into account situations where some choice options are evaluated as immoral by the individual. The utility function is then supposed to subtract moral disutility of the action from its 'intrinsic' utility. But, whatever the author may say<fnref n="22" />, in his model, values are used to assign utility to each *choice*, not to their *ordering*. The author claims to show that once a profitable but not very moral choice has been made, its intrinsic utility gradually fades while moral disutility endures, resulting in 'moral dissonance' and leading to feelings of guilt and regret. But this is independent of the utility function preceding the choice. We have to introduce a second function, post hoc, where intrinsic utility decreases over time and in which morality plays no conceptually distinct role (Gagné [2007]).

In Akerlof and Kranton [2000]'s model, it is suggested that the individual utility function takes into account a person's *identity*, knowing that it is supposed to give information about how a person would behave, in particular their propensity to follow moral norms:

$$u_i = u_i(x_i, x_{i-1}, l_i),$$

where $x_i$ and $l_i$ are i's payoff and i's identify respectively, while $x_{i-1}$ represents other individuals' payoffs.<fnref n="23" />

Other authors have tried to reconcile Andreoni ([1990], [1995])'s model of impure altruism based on a consequentialist principle with the Kantian motivational logic. For instance, Brekke, Kverdokk, and Nyborg [2003] proposed a model whose initial goal was to explain why paying people to provide a public good can crowd-out intrinsic motivations.<fnref n="24" /> In this model, each individual i has to put in some effort $e_i$ (measured in units of time) to generate a public good g. She/he has to decide how much time $l_i$ to use for leisure: $l_i = T - e_i$ (with at most T units of time are available). The total quantity of public good is $G = G_p + \sum g_i$ (where $G_p$ is the provision of the public good). The key assumption of the model is that individual i has a "morally" ideal effort ($e_i^*$) and she/he maximizes a utility function:

$$u_i = u_i(x_i, l_i) + v_i(G) + f_i(e_i, e_i^*),$$

<footnote n="22">²² He claims that in his model values correspond to 'judgments about preference orderings or about the choices that preferences have generated' (p. 232).</footnote>

<footnote n="23">²³ Sobel [2005] has proved the mathematical equivalence of this model with a previous model proposed by Stigler and Becker (1977), which is based on the idea that preferences should not be defined over marketed goods but over general commodities that people transform into consumption goods.</footnote>

<footnote n="24">²⁴ The best-known example of this 'crowding-out' effect is blood donation: paying donors reduces blood donation (Titmuss [1971]). For an excellent discussion of this case of blood donation as an illustration of how people's moral dispositions affect economic outcomes, see Hausman and McPherson ([1996], Appendix 3).</footnote>
where $u_i$ and $v_i$ are assumed increasing and concave, while the function $f_i(e_i, e_i^*)$ is assumed to attain its maximum at $e_i = e_i^*$. Assuming that all individuals share a utilitarian moral philosophy, i.e., the morally ideal effort is found by maximizing $W = \sum u_i$, the authors showed that this model is consistent with the crowding-out effect. In this model, more fundamentally, individuals are supposed to ask themselves how they should act to improve collective well-being: 'which rule of behavior would maximize collective well-being if everyone adopted the same rule as the one I plan to adopt?' This is an approximation of the Kantian categorical imperative expressed in the form of a preference rather than a pure constraint (see section 2).<fnref n="25" />

White [2004] go further by showing that it is possible to integrate Kantian morality in the form of a preference by admitting that Kantian morality includes unavoidable perfect duties (not lying, not stealing, etc.) but also other duties conceived as simple inclinations or objectives that it is desirable to adopt. Thus, Kantian economic agents differ from consequentialist agents not in the fact that they optimize, but more in *what* is to be maximized and *how* it is to be done.

In Bénabou and Tirole [2006], the authors study the agents' behaviors who choose the extent of their participation in some pro-social activity (contributing to a public good or worthy cause, engaging in a friendly action, refraining from imposing negative externalities on other, etc.). They introduced a general utility function that is taking account altruism and is motivated by a theory of social signaling, according to which people's actions are associated with reputational costs and benefits (Gintis, Smith, and Bowles [2001]). Each player selects a participation level $a$. Choosing $a$ entails a utility cost $c(a)$ and yields a monetary or other material reward $ya$. Players are assumed to be characterized by a type $v = (v_a, v_y)$, where $v_a$ is, roughly speaking, the impact of the prosocial factors associated with participation level $a$ on the agent's utility, while $v_y$ is, roughly speaking, the impact of money (consumption of market goods) on the agent's utility.<fnref n="26" />

In this model, participation at level $a$ yields a direct benefit $DB(a) = (v_a + v_y y)a - c(a)$ and a reputational benefit $RB(a) = x [\gamma_a E(v_a/a, y) - \gamma_y E(v_y/a, y)]$, where $E(v_a/a, y)$ represents the observers' posterior expectation that the player is of type $v$, given that the player chooses $a$ when the monetary incentive to choose $a$ is $y$. It is supposed that people like to be perceived as prosocial ($\gamma_a \ge 0$) and not greedy ($\gamma_y \ge 0$). Parameter $x > 0$ is representing the 'visibility' of an action (i.e., the probability that the action is visible to other players).

The utility function of Bénabou and Tirole [2006]'s model is then defined as:

$$U(a) = DB(a) + RB(a).$$

<footnote n="25">²⁵ Kessler and Leider [2012] proposed a similar model in which agents receive a disutility when they deviate from a norm.</footnote>

<footnote n="26">²⁶ They mentioned that $v_a$ is determined by at least two factors: the material payoff of the other player and the enjoyment derived from the act of giving. Thus, this model can capture Andreani's [1990] notion of warm-glow giving (see section 3).</footnote>
It should be noted that this kind of utility function can be used only in contexts in which actions are at least partially observable and decision options are defined in terms of contribution but not in terms of participation levels (e.g., in trade-off games in which agents are distributing money without themselves being affected by the distribution levels). This limits its scope of application.

Levitt and List [2007] proposed another utility function capturing moral motivations which can be applied to a wider range of situations. A utility-maximizing individual i is faced with a choice regarding one action a. The choice of action affects the agent's utility $u_i$ through two channels. The first effect is on the individual's wealth $w_i$: the higher the stakes or monetary value of the game (v), the greater the decision's impact on $w_i$. The second effect is on the moral cost or benefit $m_i$, associated with a. The authors focus on three factors that could affect the moral value of an action: (i) the negative externality that a imposes on other people; (ii) the set n of moral norms which govern behavior in the society; (iii) the extent to which actions are observed, given that the effect of scrutiny (s) is assumed to increase the moral cost.<fnref n="27" /> In their model, player i is then supposed to maximize the utility function:

$$u_i(a, v, n, s) = m_i(a, v, n, s) + w_i(a, v)^{28}$$

Alger and Weibull [2013] introduced a notion of *homo moralis* which they explicitly distinguish from the notion of *homo oeconomicus*. Again, morality is defined by taking inspiration from Kant's categorical imperative: one should make the choice that would be best is everyone took it ('universalizabilty'). More specifically, in their 2 player-model, the utility of agent i is taking the form:

$$u_i(a_1, a_2) = (1-k)\pi_i(a_1, a_2) + k\pi_i(a_1, a_1),$$

where $\pi_i$ is the payoff function of i when she chooses $a_i$ and j choices $a_j$, and where $k \in [0, 1]$. If $k = 0$, we find the classic *homo oeconomicus* case, whereas if $k = 1$, we find the *homo kantiensis* case.<fnref n="29" /> As with the models previously proposed by Brekke, Kverdokk and Nyborg [2003] or White [2004], that model represents an interesting attempt to integrate the Kantian norm in the form of a preference rather than a constraint (see section 2). However, from our point of view, it suffers from one limitation: if the payoff function is equal to the monetary payoff, then *homo moralis* preferences are just outcome-based.

<footnote n="27">²⁷ This component is taking into account that when the behavior of participants cannot be monitored, people tend to be less prosocial than when it can (for example, List [2006]).</footnote>

<footnote n="28">²⁸ This model can explain a lot of experimental regularities and the minor limitations it suffers can easily be overcome (Capraro, Halpern, and Perc [2022], p. 19). It is supposed to be concerned with social interaction models that can be described by normal-form games with monetary payments. But a similar approach was used by Lopez-Pérez [2008] with extensive-form games.</footnote>

<footnote n="29">²⁹ Alger and Weibull [2016] showed that *homo moralis* preferences are evolutionary stable, according to an appropriate definition of evolutionary stability for preferences.</footnote>
On their sides, Krupka and Weber [2013] introduced a model in which agents are torn between following their self-interest and what they believe other people would approve or disapprove of, i.e. what can be termed an 'injunctive norm' (Cappelen et al. [2007]). They assume the existence of a social norm function that associated to each action $a_j$ a number $N(a_j)$ that represents the degree of social appropriateness of that action (if $N(a_j)$ is negative, $a_j$ is viewed as socially inappropriate). The utility of player $i$ is defined as:

$$u_i(a_j) = v_i(\pi_i(a_j)) + \gamma_i N(a_j),$$

where $\pi_i(a_j)$ is the monetary payoff of agent $i$ associated with action $a_j$, $v_i$ is the utility associated to monetary payoffs, and $\gamma_i$ corresponds to the extent to which $i$ cares about doing what is socially appropriate.<fnref n="30" />

Kimbrough and Vostroknutov ([2016], [2023]) proposed a utility function similar to the one chosen by Kupta and Weber [2013]. They assume that people vacillate between maximizing material payoff and (not) doing what they think society would (dis)approve of. This corresponds to the utility function:

$$u_i(a) = v_i(\pi_i(a)) + \phi_i \eta(a),$$

where $v_i(\pi_i(a))$ is the utility from the monetary payoff $\pi_i(a)$ corresponding to action $a$, $\phi_i$ represents the extent to which agent $i$ cares about (not) doing what she thinks society would (dis)approve of, and $\eta(a)$ is a measure of the extent to which society approves or disapproves $a$. The difference with the model used by Kupta and Weber lies in the definition of $\eta$ (i.e., $N$ for these authors). Kimbrough and Vostroknutov defines that parameter in terms of cumulative dissatisfaction or regret that people experience when a certain strategy profile is realized rather than other feasible strategy profiles. Thus, in this model, the normatively best outcome is the one that minimizes aggregates regret. This implies in particular that the model fails to explain moral behaviors that are Pareto dominated, such as honesty when lying is Pareto optimal.

In a subsequent work, Capraro and Perc [2021] adopted a utility function such that people tend to follow their personal norms (i.e., what they think is morally right or wrong in a given situation) and not the injunctive norm (i.e., what they think is the moral norm common for all individuals living in the society), as in Kupta and Weber [2013] and Kimbrough and Vostroknutov ([2016], [2020]). Specifically, they assume that:

$$u_i(a) = v_i(\pi_i(a)) + \mu_i P_i(a),$$

<footnote n="30">³⁰ In addition, the authors introduce a method for measuring empirically social appropriateness, by asking experimental subjects to guess what they believe others would find socially (in)appropriate.</footnote>
where $v_i(.)$ is the utility from the monetary payoff $\pi_i(a)$ associated to action $a$, $\mu_i$ corresponds to the extent to which agent $i$ cares about doing what she thinks to be morally right, and $P_i(a)$ represents the extent to which agent $i$ thinks that $a$ is morally right.

Finally, following a logic similar to that of the three previous models, Basié and Verrina [2021] suggested retaining a more general utility function that combines personal and injunctive norms:

$$u_i(a) = v_i(\pi_i(a)) + \gamma_i N(a) + \delta_i P_i(a),$$

where $\gamma$ and $\delta$ represent the extent to which people care about following the injunctive and the personal norms, respectively.

In conclusion, each of the ‘multiple preferences’ models whose structure we have just outlined formalizes certain properties that can be attributed to moral preferences. Most of them are able of modeling non-outcome-based preferences. Unfortunately, there is currently no consensus on this issue. No ‘generic’ model of axiological rationality can therefore be deduced from these models. In reality, we are dealing with a collection of models, each addressing one aspect of axiological rationality in more or less extensive contexts.

## 5. MODELING MORALITY AS BOTH A PREFERENCE AND A CONSTRAINT: 'HIERARCHICAL PREFERENCES' MODELS

‘Hierarchical preferences’ models take a different route than ‘multiple preferences’ models. Values are no longer included in the utility function, but are used to filter out immoral preferences. Moral concerns are not in competition with material concerns; rather, they should be conceived as forming a 'preference over preferences'. The best-known model was devised by Amartya Sen (Sen [1974], [1977], [1987]).

Among the non-selfish motivations, Sen distinguishes between ‘sympathy’ and ‘commitment’. The first attitude describes a kind of second-degree egoism: the well-being of others enters directly as an argument in the utility function. The second attitude refers to the action of committing oneself to defending others’ well-being through a conscious and deliberate act, in the name of moral value. It is not to avoid regret that people act in this way, but because they place an intrinsic value on their duty and consciously decide to comply with it. Moral commitment does involve, in a very real sense, a choice contrary to preferences, which destroys the fundamental assumption that a chosen option must be better (or at least as good) as others for the person who chooses it<fnref n="31" />.

<footnote n="31">³¹ See also Gibbard [1990] for a “norm expressivist” analysis seeking to shed light on rationality and morality which can be compared to that carried out by Sen. According to Gibbard, moral norms also are norms for how to feel given full engagement.</footnote>
According to Sen, the utility function simply cannot express moral choice. He then develops the concepts of 'system of preferences' and 'moral meta-ranking' between actions. Each person is assigned a single preference ordering and, as needs arise, this ordering is supposed to reflect her/his interests, represent her/his well-being, summarize her/his opinion of what is the right thing to do, and describe that choice and her/his actual behavior. Can a single preference ordering fulfill all these roles? Sen does not think so. He therefore proposes to accept the existence of several orders of preference, each ordering actions according to strong but distinct motivations. He then puts forward the hypothesis that we implicitly order all these rankings according to a 'moral view' (Sen [1974]). More precisely, this would be a meta-ranking according to a lexicographical order, decreasing from the most satisfying order to the least satisfying of all from an ethical perspective. The key point is that this meta-ranking is lexicographic in terms of the degree of morality, and not in terms of the hoped-for utility it secures. The procedure ends when the model selects a single maximum choice.

This metaphor thus allows for varying degrees of morality in every one of us. But it is hard to imagine that this decision-making procedure can be applied to most of our everyday choices, when the distinction between morality and self-interest is not all that clear. We are then faced with what the philosopher John Rawls called the 'strains of commitment' (Rawls [1971], p. 145, 176). In order to meet this need for moral compromise, then Sen suggests we simply bypasses some preferences at the top of the final ranking by opting for a decision lower down the ranking (Sen [1977]).

Sen was one of the first authors to propose a discussion of the problems raised by the requirements imposed on individual optimization modeling by the existence of a moral commitment. But his discussion of morality remains largely verbal; he does not propose a model in the mathematical sense of the term, but rather a set of guidelines for building such a model. And, what's more, he did not exploit the full potential of these intuitions; in particular, he did not clearly draw all the consequences of the lexicographical character of the individual optimization procedure, which is a central feature of moral commitment.

In a more structured framework, Arnsperger [1998] showed that, unfortunately this model of hierarchical preferences is not in itself able of managing the moral compromise; indeed, some function of additive utilities is required. That obviously limits the interest of that approach for modeling axiological rationality. For it could be replaced by a model of additive utilities in which
moral imperatives ranked highest by the agent would be conceived as infinitely inelastic goods
(Brennan [1989], p. 200).<fnref n="32" />

6. CONCLUSION

This paper reveals the various obstacles encountered when attempting to model axiological rationality in economics. We suggest that three main modeling methods have been implicitly developed in the literature: as a constraint ('constraint-based approach'), as a preference ('preference-based approach'), or both as a preference and a constraint ('hybrid approach'). The first approach aims to reconcile the Kantian 'universalistic' norm with rational choice theory. We argue that modeling morality as a mere constraint seems far from our current ethical intuitions. Yet, from an epistemological point of view, this approach has the advantage of maintaining unity in the modeling of decisions in rational choice theory. For other authors, morality intervenes directly in the agent's preference system ('preference-based approach'). Some work in this insight are strongly influenced by 19th century Scottish authors David Hume and Adam Smith, with emotions playing a central role in people's behavior: they assume that people have *social preferences*, in that their utility function depends not just on their payoffs but also on the payoffs of others ('other-regarding preferences'). We argue that behavioral models that illustrate this approach open up an interesting line of research for explaining some pro-social, cooperative or altruistic behaviors into economics by integrating a variety of social emotions in rational decisions. Yet, in these economic models based primarily on psychological factors, preferences remain essentially outcome-based. Another trend in research attributes a special characterization to *moral preferences*, by recognizing that morality cannot be reduced to altruism or sympathy. Moral concerns are explicitly involved in the models. 'Multiple preferences' models search for compromise between moral preferences and more material ones. In most of these models, it is worth noting that preferences are typically non-outcome-based, and so better suited to formalizing an axiologically rational behavior. 'Hierarchical preferences' models take a different route than 'multiple preferences' models. Values are no longer included in the utility function but are used to filter out immoral preferences. Moral concerns are not in competition with material concerns; rather, they should be conceived as forming a 'preference over preferences'. The conceptual framework adopted is appealing in that it embodies a "hybrid" approach in which morality is seen both as a preference and a constraint. Unfortunately, it can be shown this approach, as it stands, has nothing special to offer in the perspective of *modeling* axiological rationality.

<footnote n="32">³² Walliser [2001] and Gagné [2007] reached the same conclusion.</footnote>
In conclusion, given the strengths and weaknesses of the different approaches examined in our paper, we can claim that ‘multiple preferences’ models certainly offer the most appropriate properties for modeling axiological rationality. However, the high degree of heterogeneity in this class of ‘multiple preferences’ models leads us to advance that it is probably illusory to hope for a “generic” model for axiological rationality in economics. But is that surprising? Not really, no. We come across a difficulty already present in behavioral economics where ‘quasi-rationality’ (in the sense of Thaler [1994]) is in fact embodied in a myriad of models including prospect theory, the hyperbolic discount model, bounded rationality models of game (e.g., cognitive hierarchy model), learning models (e.g., experience-weighted attraction models) or social preference models, to name just the most representative classes of models.<fnref n="33" /> Yet, that’s where the similarities end. ‘Quasi-rational’ models, indeed, are perhaps not as radically opposed to the standard rational model of economic theory as they might seem: models remain output-based and basically boil down to adding parameters that are supposed to take into account a set of various psychological phenomena hitherto ignored.<fnref n="34" /> With ‘multiple preferences’ models, in contrast, we are faced with a collection of models reporting on non-output-based preferences whose deontological nature differs fundamentally from that of the standard rational model, each illustrating an aspect of axiological rationality in more or less large context. These new models — which it would certainly be useful to divide into several more homogeneous classes — broaden the scope of economic theory by proposing explanations for a lot of empirical or experimental observed behaviors which, until now, have escaped models proposed by both rational choice theory and behavioral economics. Such behaviors, which do not appear to serve any identifiable interest, can no longer be accused of being irrational or simply the result of errors or misunderstanding.

<footnote n="33">³³ For a simplified presentation and discussion of such models, please refer in particular to Serra [2017].</footnote>

<footnote n="34">³⁴ Of course, this commentary by no means exhausts the contemporary thinking about rationality in economics, leaving aside more precisely the position of the minority current of behavioral economics that has developed around the experimental psychologist Gerd Gigerenzer with his notion of 'ecological' rationality (Gigerenzer and Goldstein [1996], for instance). More in line with Herbert Simon's original vision of bounded rationality in its procedural dimension (Simon [1955]), these authors defend the 'rational' nature of human behavior, provided the environment in which it takes place is taken into account. It is only in the link between cognition — at the individual level — and the environment — at the aggregate level — that rationality can be properly conceptualized; cognition can only be 'social'. In this respect, this line of thought is similar to that of an experimentalist like Vernon Smith, who today also advocates an 'ecological' approach to rationality, which he contrasts with 'constructivist' rationality (Smith [2008]). See Serra [2022] for more details on this issue.</footnote>
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CEE-M Working Papers<fnref n="1" /> - 2025

WP 2025-01 **Katrin Erdlenbruch, Mabel Tidball & Julia de Frutos Cachorro** « Resource extraction and land-use choice in a two-player two-period game »

WP 2025-02 **Gabriel Bayle & Marc Willinger** « Efficiency of the Minimum Approval Mechanism with heterogeneous players »

WP 2025-03 **Karine Constant, Marion Davin & Emmanuelle Lavaine** « Does income inequality influence health vulnerability to pollution? Evidence from France »

WP 2025-04 **Denis Claude & Mabel Tidball** « Revisiting Stackelberg in his own light »

WP 2025-05 **Gabriel Bayle, Dimitri Dubois & Marc Willinger** « L'économie à l'ère de la science ouverte : un nouvel élan pour la reproductibilité»

WP 205-06 **Daniel Serra & Adda Benslimane** « L'économie à l'ère de la science ouverte : un nouvel élan pour la reproductibilité»

<footnote n="1">¹ CEE-M Working Papers / Contact : laurent.garnier@inrae.fr</footnote>

<footnote>• RePEc https://ideas.repec.org/s/hal/wpceem.html</footnote>

<footnote>• HAL https://halshs.archives-ouvertes.fr/CEE-M-WP/</footnote>