to open a way

It is true that the classic origins of the doctrine of virtue later made Christian critics suspicious of it. They warily regarded it as too philosophical and not Scriptural enough. Thus, they preferred to talk about commandments and duties rather than about 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. The doctrine of virtue, that is, is one form of the doctrine of obligation, but one by nature free of regimentation and restriction. On the contrary, its aim is to clear a trail, to open a way.

Josef Pieper, in his The Four Cardinal Virtues of 1966. He ends his preface by speaking to the reader this way:

The interpreter [of these virtues], in these latter days, invokes this tradition in the hope of seeming less ridiculous as he boldly drafts a moral standard for humanity which he, in his own daily life, is utterly unable to meet.