As Michael Slote (1984) has rightly pointed out, “ordinary moral thinking seems to involve an asymmetry regarding what an agent is permitted to do to himself and what he is permitted to do to others.” For one, agents are permitted to sacrifice their own greater good in order to secure a lesser net benefit for others, but not permitted to sacrifice someone else’s greater good in order to secure a lesser net benefit for others. For another, whereas it seems morally permissible to allow yourself to suffer unnecessarily, it seems morally impermissible to allow someone else to suffer unnecessarily. To make this a bit more concrete, consider the following illustrations. First, whereas it seems morally permissible to cut off my right arm in order to save someone else’s pinky finger, it seems morally wrong to cut off someone else’s right arm (even with his or her consent) in order to save yet another person’s pinky finger. Second, whereas it seems imprudent but not immoral of me to negligently leave thumbtacks on the ground where only I tread, it seems wrong of me to negligently leave thumbtacks on the ground where others tread.
Now what exactly is the nature of this asymmetry? I propose that it’s this: