Supererogation is a difficult concept for me. But there has to be such a thing. If Jones has suffered two hundred weeks of torture to save the lives of two hundred strangers, and then declines the 201st week of torture to save the life of the 201st stranger, Jones does not do wrong. And if he were to accept the torture, he would be acting superegatorily (barring special circumstances).
I doubt the following account is in the end right, but I think it is surprisingly defensible (modulo perhaps some minor tweaks):
- An action is supererogatory if and only if it is permissible and less convenient than some available alternative permissible action.
The account above seems to be subject to simple counterexamples. Let's say it's permissible for me to go to the kitchen, and suppose there are two paths—an easier and a harder one. Then surely both paths are permissible, and the harder one is less convenient, but that doesn't make the less convenient one supererogatory!
To respond I note that it is wrong to pointlessly impose burdens on any person—including oneself. (Argument 1: We are to love all of the people that God loves, and love prohibits pointless imposition of burdens. But I am one of the people God loves. So I am not permitted to impose pointless burdens on myself. Argument 2: What is vicious is impermissible. But pointless imposition of burdens on myself is contrary to the virtues of prudence and hence vicious.) Thus if there is no benefit to anybody from taking the harder path, the harder path is not permissible, and hence is not supererogatory. But suppose that there is a benefit to someone from the harder path: maybe I become physically or morally stronger, or maybe someone else benefits in some way. Then as long as the harder path is permissible (if the benefit is too trivial as compared to the burden, it might not be), it does seem to be supererogatory.
I do suspect that this account of supererogation only stands a chance if we have duties to self, but that's not a weakness of it.
Some people doubt that there are any supererogatory actions. On the above account, it is quite plausible that there are. First, we need to note that surely there are cases where we choose between multiple permissible actions. And second we note that it is very likely that among such choices there are going to be cases where the permissible options are not all equally convenient. And then the less convenient ones will be supererogatory.
Note that if convenience is what is given up in self-sacrifice, then every supererogatory action involves self-sacrifice. Now, self-sacrifice is relative to some alternative that does not involve such a sacrifice. We might then rephrase our definition of supererogation as:
- An action is supererogatory if and only if it is permissible and it is a self-sacrifice relative to some permissible alternative.
Go back to my initial case of Jones. If Jones did undergo the 201st week of torture, he would be doing something permissible, but it would also be permissible for him not to undergo that torture. However, undergoing the torture is less convenient. Again, this sounds like an absurd understatement, but in our technical sense of "convenient", it's not. It sounds a lot better in the language of self-sacrifice: Jones' undergoing the torture is permissible and is a self-sacrifice relative to the alternative of not undergoing it.
I think the weakness of the account is it does not make clear why supererogation is particularly praiseworthy. Moreover, even if the account happens to be extensionally correct, I don't think it captures what it is that grounds supererogation.