ABSTRACT
Although the usual framework of decision theory may not be an adequate representation of the psychological states of agents, it does provide a way of making some of these points more precise, and eliciting some of the nuances of the notion of psychological altruism. Let's say that a valuational structure (or valuation) for an agent is a set of alternative actions that the agent takes to be available and a mapping from that set to the real numbers, so that the number assigned to an option represents the value the agent attaches to the expected outcome of performing that action; or, more generally, when the circumstances involve interactions, the valuation identifies sets of alternatives for all the agents involved in the interaction, and maps each combination of actions to expected values for all the agents. 3 We can now introduce a notion of psychological altruism as follows:
The valuational structure that A forms in situation C is weakly altruistic with respect to B just in case: (1) in C, A ranks Oi ahead of Oj (2) in C*, which is like C except only in the fact that
the actions available to A have no impact on the wellbeing ofB, A would rank the analogue of Oj, 0; ahead ofthe analogue of 0i, 0:
(4) A's ranking of Oi ahead of Oj is independent of A's expectations about B's future actions (and, in particular, about actions that would benefit A).
