Everyone is entitled to commit murder in the imagination once in a while, not to mention lesser infractions. - Thomas Nagel

To look for a single general theory of how to decide the right thing to do is like looking for a single theory of how to decide what to believe.

We assume that our own advances in objectivity are steps along a path that extends beyond them and beyond all our capacities. But even allowing unlimited time, or an unlimited number of generations, to take as many successive steps as we like, the process can never be completed. … What is wanted is some way of making the most objective standpoint the basis of action.

Common sense doesn't have the last word in ethics or anywhere else, but it has, as J. L. Austin said about language, the first word: it should be examined before it is discarded.