Saving and Letting Live

There is a metaphysical difference between person A killing person B and A merely letting B die. There is also a metaphysical difference between A saving B and A merely letting B live. This paper argues that the metaphysical difference between saving and letting live gives rise to a moral difference. It then puts that moral difference to work: for example, it accounts for the long-felt moral difference between failing to rescue a drowning child and failing to donate $4000 to Oxfam (sufficient for them, in the aggregate, to prevent a child's death).