Utilitarianism is the iea that the moral worth of an action is solely determined by its contribution to overall utility, that is, its contribution to happiness or pleasure as summed among all persons. It is thus a form of consequentialism, meaning that the moral worth of an action is determined by its outcome—the ends justify the means. Utility — the good to be maximized — has been defined by various thinkers as happiness or pleasure (versus sadness or pain), though preference utilitarians like Peter Singer define it as the satisfaction of preferences. It may be described as a life stance with happiness or pleasure as ultimate importance.