Full Idea
The doctrine of double effect says that it is legitimate to do harm if the harm is the unintended side-effect of an effort to achieve a legitimate goal.
Gist of Idea
It is legitimate to do harm if it is the unintended side-effect of an effort to achieve a good
Source
A.C. Grayling (Among the Dead Cities [2006], Ch.6)
Book Reference
Grayling,A.C.: 'Among the Dead Cities' [Bloomsbury 2006], p.215
A Reaction
I think a key principle of morality is our duty to think about possible unnoticed consequences of our actions. To neglect concern for side-effects is wicked. Beyond that, the issue must concern the particulars of the situation.