Further, even among the other virtues one ranks higher than another. But in order that a virtue be principal, it needs not to rank above all the others, but above some. Therefore it seems that there are many more principal virtues. In like manner, we find the same number if we consider the subjects of virtue. Reply to Objection 1.
Prudence is the principal of all the virtues simply.
The others are principal, each in its own genus. Reply to Objection 2. That part of the soul which is rational by participation is threefold, as stated above. Reply to Objection 3. All the other virtues among which one ranks before another, are reducible to the above four, both as to the subject and as to the formal principle.