Full Idea
It would be impossible to have only one virtue, unless it were a very trivial one such as thrift.
Gist of Idea
Only trivial virtues can be possessed on their own
Source
Iris Murdoch (The Sovereignty of Good [1970], III)
Book Reference
Murdoch,Iris: 'The Sovereignty of Good' [RKP 1974], p.95
A Reaction
A nicely nuanced commitment to the unity of virtue. You might exhibit courage alone in a brute animal way, but the sort of courage we all admire is part of more extended virtues.