Discussions of altruism occur in three importantly different contexts. During the past four decades, evolutionary theory has been concerned with the possibility that forms of behaviour labelled as altruistic could emerge and could be maintained under natural selection. In these discussions, an agent A is said to act altruistically towards a beneficiary B when A's action promotes the expected reproductive success of B at expected reproductive cost to A. This sort of altruism, biological altruism, is quite different from the kind of behaviour important to debates about ethical and social issues. There the focus is on psychological altruism, a notion that is concerned with the intentions of the agent and that need have no connection with the spread of anyone's genes. Psychological altruists are people with other-directed desires, emotions or intentions (this is a rough preliminary characterization, to be refined below). Finally, in certain kinds of social scientific research, the important concept is that of behavioural altruism. From the outside, behavioural altruists look like psychological altruists, although their motives and preferences may be very different.

To understand the human capacity for psychological altruism, one requires a proper understanding of how people actually think and feel. This paper addresses the possible relevance of recent findings in experimental economics and neuroeconomics to the philosophical controversy over altruism and egoism. After briefly sketching and contextualizing the controversy, we survey and discuss the results of various studies on behaviourally altruistic helping and punishing behaviour, which provide stimulating clues for the debate over psychological altruism. On closer analysis, these studies prove less relevant than originally expected because the data obtained admit competing interpretations – such as people seeking fairness versus people seeking revenge. However, this mitigated conclusion does not preclude the possibility of more fruitful research in the area in the future. Throughout our analysis, we provide hints for the direction of future research on the question.

How do we determine the well-being of a person when her preferences are not stable across worlds? Suppose, for instance, that you are considering getting married, and that you know that if you get married, you will prefer being unmarried, and that if you stay unmarried, you will prefer being married. The general problem is to find a stable standard of well-being when the standard is set by preferences that are not stable. In this paper, I shall show that the problem is even worse: inconsistency threatens if we accept both that your desires determine what is good for you and that you must prefer what is better for you. After I have introduced a useful toy model and stated the inconsistency argument, I will go on to discuss a couple of unsuccessful theories and see what we can learn from their mistakes. One important lesson is that how you would have felt about a life had you never led it is irrelevant to the question of how good that life is for you. What counts is how you feel about your life when you are actually leading it. Another lesson is that a life can be better for you even if you would not rank it higher, if you were to lead it.

People sometimes think in terms of ‘we’ referring to a group they belong to. When making decisions, they frame the decision problem as: ‘What should we do?’ instead of ‘What should I do?’. We study one particular approach to such ‘we-reasoning’, economist Michael Bacharach's theory of ‘team reasoning’, and relate it to philosopher Raimo Tuomela's distinction between ‘I-mode’ reasoning and ‘we-mode’ reasoning. We argue that these theories complement each other: Tuomela's philosophical theory provides a conceptual framework augmenting Bacharach's theory, and Bacharach's mathematical results support Tuomela's view on the irreducibility of the we-mode to the I-mode. We-mode reasoning can explain some kinds of human cooperative behaviour left unexplained by standard game theory. Standard game theory is not well-equipped to deal with we-mode reasoning but it can be extended by the methods developed by Bacharach. However, we argue that both standard game theory and Bacharach's theory require more attention to the information-sharing stages that precede actual decision making, and we describe a stage-based model of we-reasoning.

The adequacy of currently popular accounts of the genetic basis for psychological altruism, including inclusive fitness (kin selection), reciprocal altruism, sociality, and group selection, is questioned. Problems exist both with the evidence cited as supporting these accounts and with the relevance of the accounts to what is being explained. Based on the empathy-altruism hypothesis, a more plausible account is proposed: generalized parental nurturance. It is suggested that four evolutionary developments combined to provide a genetic basis for psychological altruism. First is the evolution in mammals of parental nurturance. Second is the evolution in humans (and possibly a few other species) of the ability to see others as sentient, intentional agents and, thereby, to recognize other's needs, even subtle ones. Third is the evolution in humans of tender, empathic emotions as an important component of parental nurturance. Fourth is the evolution in humans of cognitive capacities that make it possible to generalize tender, empathic feelings and, thereby, altruism beyond offspring.

To a practitioner in the social sciences, game theory primarily helps to identify situations in which interdependent decisions are somehow problematic; solutions often require venturing into the social sciences. Game theory is usually about anticipating each other's choices; it can also cope with influencing other's choices. To a social scientist the great contribution of game theory is probably the payoff matrix, an accounting device comparable to the equals sign in algebra.

In this paper, we examine different forms of altruism. We commence by analysing the ‘behavioural’ definition and, after clarifying its conditions for altruism, we argue that it is not in ‘reflective equilibrium’ with everyday linguistic usage of the term. We therefore consider a ‘psychological’ definition, which we likewise refine, and argue that it better reflects ordinary language use. Both behavioural and psychological approaches define altruism descriptively and thus fail to capture an important aspect of altruism, namely its normative component. Altruism, we argue, is a ‘thick concept’, i.e. one which embodies both positive and normative components. We discuss and compare various formulations of this normative component.

This paper argues that measurements of opportunity which focus on the contents of a person's opportunity set fail to capture open-ended aspects of opportunity that liberals should value. I propose an alternative conception of ‘opportunity as mutual advantage’ which does not require the explicit specification of opportunity sets, and which rests on an understanding of persons as responsible rather than rational agents. I suggest that issues of distributive fairness are best framed in terms of real income, and that meaningful measurements of real income are possible if opportunity as mutual advantage is ensured.

This essay criticizes the proposal recently defended by a number of prominent economists that welfare economics be redirected away from the satisfaction of people's preferences and toward making people happy instead. Although information about happiness may sometimes be of use, the notion of happiness is sufficiently ambiguous and the objections to identifying welfare with happiness are sufficiently serious that welfare economists are better off using preference satisfaction as a measure of welfare. The essay also examines and criticizes the position associated with Daniel Kahneman and a number of co-authors that takes welfare to be ‘objective happiness’ – that is, the sum of momentary pleasures.

Much of economics is built on the assumption that individuals are driven by self-interest and economic development is an outcome of the free play of such individuals. On the few occasions that the existence of altruism is recognized in economics, the tendency is to build this from the axiom of individual selfishness. The aim of this paper is to break from this tradition and to treat as a primitive that individuals are endowed with the ‘cooperative spirit’, which allows them to work in their collective interest, even when that may not be in their self-interest. The paper tracks the interface between altruism and group identity. By using the basic structure of a Prisoner's Dilemma game among randomly picked individuals and building into it assumptions of general or in-group altruism, the paper demonstrates how our selfish rationality interacts with our innate sense of cooperation. The model is used to outline circumstances under which cooperation will occur and circumstances where it will break down. The paper also studies how sub-groups of a society can form cooperative blocks, whether to simply do better for themselves or exploit others.

In this paper I study intentions of the form ‘I intend that we . . .’, that is, intentions with a we-content, and their role in interpersonal coordination. I focus on the notion of epistemic support for such intentions. Using tools from epistemic game theory and epistemic logic, I cast doubt on whether such support guarantees the other agents' conditional mediation in the achievement of such intentions, something that appears important if intentions with a we-content are to count as genuine intentions. I then formulate a stronger version of epistemic support, one that does indeed ensure the required mediation, but I then argue that it rests on excessively strong informational conditions. In view of this I provide an alternative set of conditions that are jointly sufficient for coordination in games, and I argue that these conditions constitute a plausible alternative to the proposed notion of epistemic support.

Egoism and altruism are unequal contenders in the explanation of human behaviour. While egoism tends to be viewed as natural and unproblematic, altruism has always been treated with suspicion, and it has often been argued that apparent cases of altruistic behaviour might really just be some special form of egoism. The reason for this is that egoism fits into our usual theoretical views of human behaviour in a way that altruism does not. This is true on the biological level, where an evolutionary account seems to favour egoism, as well as on the psychological level, where an account of self-interested motivation is deeply rooted in folk psychology and in the economic model of human behaviour. While altruism has started to receive increasing support in both biological and psychological debates over the last decades, this paper focuses on yet another level, where egoism is still widely taken for granted. Philosophical egoism (Martin Hollis’ term) is the view that, on the ultimate level of intentional explanation, all action is motivated by one of the agent's desires. This view is supported by the standard notion that for a complex of behaviour to be an action, there has to be a way to account for that behaviour in terms of the agent's own pro-attitudes. Psychological altruists, it is claimed, are philosophical egoists in that they are motivated by desires that have the other's benefit rather than the agent's own for its ultimate object (other-directed desires). This paper casts doubt on this thesis, arguing that empathetic agents act on other people's pro-attitudes in very much the same way as agents usually act on their own, and that while other-directed desires do play an important role in many cases of psychologically altruistic action, they are not necessary in explanations of some of the most basic and most pervasive types of human altruistic behaviour. The paper concludes with the claim that philosophical egoism is really a cultural value rather than a conceptual feature of action.