Objection 1: It would seem that moral can be without intellectual virtue. Because moral virtue, as Cicero says (De Invent. Rhet. ii) is "a habit like a second nature in accord with reason." Now though nature may be in accord with some sovereign reason that moves it, there is no need for that reason to be united to nature in the same subject, as is evident of natural things devoid of knowledge. Therefore in a man there may be a moral virtue like a second nature, inclining him to consent to his reason, without his reason being perfected by an intellectual virtue.
Obj. 2: Further, by means of intellectual virtue man obtains perfect use of reason. But it happens at times that men are virtuous and acceptable to God, without being vigorous in the use of reason. Therefore it seems that moral virtue can be without intellectual.
Obj. 3: Further moral virtue makes us inclined to do good works. But some, without depending on the judgment of reason, have a natural inclination to do good works. Therefore moral virtues can be without intellectual virtues.
On the contrary, Gregory says (Moral. xxii) that "the other virtues, unless we do prudently what we desire to do, cannot be real virtues." But prudence is an intellectual virtue, as stated above (Q. 57, A. 5). Therefore moral virtues cannot be without intellectual virtues.
I answer that, Moral virtue can be without some of the intellectual virtues, viz. wisdom, science, and art; but not without understanding and prudence. Moral virtue cannot be without prudence, because it is a habit of choosing, i.e. making us choose well. Now in order that a choice be good, two things are required. First, that the intention be directed to a due end; and this is done by moral virtue, which inclines the appetitive faculty to the good that is in accord with reason, which is a due end. Secondly, that man take rightly those things which have reference to the end: and this he cannot do unless his reason counsel, judge and command aright, which is the function of prudence and the virtues annexed to it, as stated above (Q. 57, AA. 5, 6). Wherefore there can be no moral virtue without prudence: and consequently neither can there be without understanding. For it is by the virtue of understanding that we know self-evident principles both in speculative and in practical matters. Consequently just as right reason in speculative matters, in so far as it proceeds from naturally known principles, presupposes the understanding of those principles, so also does prudence, which is the right reason about things to be done.
Reply Obj. 1: The inclination of nature in things devoid of reason is without choice: wherefore such an inclination does not of necessity require reason. But the inclination of moral virtue is with choice: and consequently in order that it may be perfect it requires that reason be perfected by intellectual virtue.
Reply Obj. 2: A man may be virtuous without having full use of reason as to everything, provided he have it with regard to those things which have to be done virtuously. In this way all virtuous men have full use of reason. Hence those who seem to be simple, through lack of worldly cunning, may possibly be prudent, according to Matt. 10:16: "Be ye therefore prudent (Douay: 'wise') as serpents, and simple as doves."
Reply Obj. 3: The natural inclination to a good of virtue is a kind of beginning of virtue, but is not perfect virtue. For the stronger this inclination is, the more perilous may it prove to be, unless it be accompanied by right reason, which rectifies the choice of fitting means towards the due end. Thus if a running horse be blind, the faster it runs the more heavily will it fall, and the more grievously will it be hurt. And consequently, although moral virtue be not right reason, as Socrates held, yet not only is it "according to right reason," in so far as it inclines man to that which is, according to right reason, as the Platonists maintained [*Cf. Plato, Meno xli.]; but also it needs to be "joined with right reason," as Aristotle declares (Ethic. vi, 13).