From the Prologue of The Four Cardinal Virtues

To define the obligations of man is certainly a legitimate, even estimable, and no doubt necessary undertaking. With a doctrine of commandments or duties, however, there is always the danger of arbitrarily drawing up a list of requirements and losing sight of the human person who "ought" to do this or that. The doctrine of virtue, on the other hand, has things to say about this human person; it speaks both of the kind of being which is his when he enters the world, as a consequence of his createdness, and the kind of being he ought to strive toward and attain to - by being prudent, just, brave, and temperate.

~Josef Pieper, The Four Cardinal Virtues