Very few people deliberately do what, at the moment, they believe to be wrong; usually they first argue themselves into a belief that what they wish to do is right. They decide that it is their duty to teach so-and-so a lesson, that their rights have been grossly infringed that if they take no revenge there will be an encouragement to injustice, that without a moderate indulgence in pleasure a character cannot develop in the best way, and so on and so on.

Bertrand Russell, ‘The Elements of Ethics’, in Philosophical Essays, 1910, sect. 21