Full Idea
Virtue is the strength of man's maxims in fulfilling his duty.
Gist of Idea
Virtue is strong maxims for duty
Source
Immanuel Kant (Metaphysics of Morals II:Doctrine of Virtue [1797], 394 Intro IX)
Book Reference
Kant,Immanuel: 'The Metaphysics of Morals', ed/tr. Gregor,Mary [CUP 1991], p.197
A Reaction
So virtue is just strong moral commitment. So what are we to make of the lists of distinctive virtues, found in every culture? How do they differ? Only in the areas of duty to which they refer? How do we possess some virtues without others?