I want to discuss a problem that is thrown up by all varieties of utilitarianism: act and rule utilitarianism, average and aggregate, cardinal and ordinal. It is this: why should individual want satisfaction be the criterion of justice and social choice when individual wants themselves may be shaped by a process that preempts the choice? And, in particular, why should the choice between feasible options only take account of individual preferences if people tend to adjust their aspirations to their possibilities? For the utilitarian, there would be no welfare loss if the fox were excluded from consumption of the grapes, since he thought them sour anyway. But of course the cause of his holding the grapes to be sour was his conviction that he would be excluded from consumption of them, and then it is difficult to justify the allocation by reference to his preferences.

I shall refer to the phenomenon of sour grapes as adaptive preference formation (or adaptive preference change, as the case may be). Preferences shaped by this process I shall call adaptive preferences. The analysis of this mechanism and of its relevance for ethics will proceed in three steps. Section I is an attempt to circumscribe the phenomenon from the outside, by comparing it with some other mechanisms to which it is closely related and with which it is easily confused. Section II is an analysis of the fine grain of adaptive preferences, and proposes some criteria by which they may be distinguished from other preferences. And section III is a discussion of the substantive and methodological implications of adaptive preference formation for utilitarianism, ethics and justice.