Duty and permission for utilitarians

In ethics, some reasons for action have more justifying force (tending to render an action permissible) than requiring force (tending to render an action obligatory). Notably, the fact that a socially beneficial action would entail significant self-sacrifice often provides one with a justification to refrain, without producing any requirement to refrain. At the same time, in similar circumstances, the fact that a socially beneficial action would require imposing significant sacrifices on others may produce a moral requirement to refrain. I offer a rule utilitarian account of this, according to which the recognition of justifying reasons to refrain from self-sacrifice functions as a kind of concession that an optimal system of social rules must make to human partiality to avoid widespread resistance and circumvention of the rules. In such a system, we also have justifications for sacrificing third parties for the sake of maximizing utility in just those situations in which a practice of so sacrificing third parties would create benign rather than perverse incentives. I go on to consider why there are limits to how low the demands of morality may be (for extremely selfish people), as well as limits to how much personal sacrifice one may make for the sake of others (for extremely altruistic people).