Men ought to be unselfish, ought to be fair. Not that men are unselfish, not that they like being unselfish, but that they ought to be.
 C. S. Lewis, Mere Christianity (1952). copy citation

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Author C. S. Lewis
Source Mere Christianity
Topic
Date 1952
Language English
Reference
Note Adapted from a series of BBC radio talks made between 1942 and 1944
Weblink https://www.dacc.edu/assets/pdfs/PCM/merechristianitylewis.pdf

Context

“all you are really saying is that decent behaviour is decent behaviour. You would have said just as much if you had stopped at the statement, ‘Men ought to be unselfish.’ And that is where I do stop. Men ought to be unselfish, ought to be fair. Not that men are unselfish, not that they like being unselfish, but that they ought to be. The Moral Law, or Law of Human Nature, is not simply a fact about human behaviour in the same way as the Law of Gravitation is, or may be, simply a fact about how heavy objects behave. On the other hand, it is not a mere fancy, for we cannot get rid of the idea, and most of the things we say and think about men would be reduced to nonsense if we did.” source