Duties to address severe deprivation based on being able to assist at some cost—assistance-based duties—are commonly thought (correctly, it is assumed in this paper) to be much less stringent than duties to address severe deprivation based on having contributed to its occurrence—contribution-based duties.

This essay explores the implications of failing to discharge one’s assistance-based duties, and tries to undermine the assumption that such failures are not very morally significant because such duties are not stringent. It takes up this task by considering how much additional cost a person who failed to comply with his assistance-based duty at one time would be morally required to take on to avert the same misfortune by that same person at a later time. It concludes that, like contribution-based duties, the duties to assist of those who have earlier failed to assist can be quite demanding indeed—and can be enforced through the proportionate use of force.