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.
The evolution of utility functions and psychological altruism
