Aristotle, Nicomachean Ethics
H. Rackham, Ed.

all the virtues are forms of Prudence, but right in saying that they cannot exist without Prudence. [4] A proof of this is that everyone, even at the present day, in defining Virtue, after saying what disposition it is¹ and specifying the things with which it is concerned, adds that it is a disposition determined by the right principle; and the right principle is the principle determined by Prudence. It appears therefore that everybody in some sense, divines that Virtue is a disposition of this nature, namely regulated by Prudence. [5] This formula however requires a slight modification. Virtue is not merely a disposition conforming to right principle, but one cooperating with right principle; and Prudence is right principle² in matters of conduct. Socrates then thought that the virtues are principles, for he said that they are all of them forms of knowledge. We on the other hand say that the virtues cooperate with principle. [6]

These considerations therefore show that it is not possible to be good in the true sense without Prudence, nor to be prudent without Moral Virtue.

（Moreover, this might supply an answer to the dialectical argument that might be put forward to prove that the virtues can exist in isolation from each other, on the ground that the same man does not possess the greatest natural capacity for all of them, so that he may have already attained one when he has not yet attained another. In regard to the natural virtues this is possible;