Instrumental rationality and ethics of motive
What kind of instrumental rationality is associated with economic welfare theories based on the ethics of motive? In general, when we judge that a thing is good by reference to its consequences, we recognize that it is instrumental to an end. Rationality here is an instrument that coordinates the means with the ends, because those ends cannot be achieved if the decision maker fails to value the actions or instruments for pursuing them. A dispute about means is not an ethical one, but has to be solved on a purely scientific basis (Russell, 1954, p. 101); it consists of deductions from a series of postulates.
As for economic welfare theories based on the ethics of motive considered here, an action is approved or disapproved according to whether it increases or decreases utility. Therefore, the sole rational criterion of choice is the maximization of the expected utility (MEU). Let us assume that the possible events ex, i = 1 ... n, are mutually exclusive and exhaustive alternatives: utility vi is associated with each of them. Until an event has happened, it is uncertain what value the utility will take, and therefore it is assumed that the probability pi of each event is known.
The sum of the weighted utilities, ^p , is the expected value, which has to be maximized by rational agents.