Objection 1. It would seem that every virtue is a moral virtue. Because moral virtue is so called from the Latin "mos," i.e. custom. Now, we can accustom ourselves to the acts of all the virtues. Therefore every virtue is a moral virtue.
Objection 2. Further, the Philosopher says (Ethic. ii, 6) that moral virtue is "a habit of choosing the rational mean." But every virtue is a habit of choosing: since the acts of any virtue can be done from choice. And, moreover, every virtue consists in following the rational mean in some way, as we shall explain further on (64, A1,2,3). Therefore every virtue is a moral virtue.
Objection 3. Further, Cicero says (De Invent. Rhet. ii) that "virtue is a habit like a second nature, in accord with reason." But since every human virtue is directed to man's good, it must be in accord with reason: since man's good "consists in that which agrees with his reason," as Dionysius states (Div. Nom. iv). Therefore every virtue is a moral virtue.
On the contrary, The Philosopher (Ethic. i, 13): "When we speak of a man's morals, we do not say that he is wise or intelligent, but that he is gentle or sober." Accordingly, then, wisdom and understanding are not moral virtues: and yet they are virtues, as stated above (Question 57, Article 2). Therefore not every virtue is a moral virtue.
I answer that, In order to answer this question clearly, we must consider the meaning of the Latin word "mos"; for thus we shall be able to discover what a "moral" virtue is. Now "mos" has a twofold meaning. For sometimes it means custom, in which sense we read (Acts 15:1): "Except you be circumcised after the manner (morem) of Moses, you cannot be saved." Sometimes it means a natural or quasi-natural inclination to do some particular action, in which sense the word is applied to dumb animals. Thus we read (2 Maccabees 1:2) that "rushing violently upon the enemy, like lions [Leonum more, i.e. as lions are in the habit of doing], they slew them": and the word is used in the same sense in Psalm 67:7, where we read: "Who maketh men of one manner [moris] to dwell in a house." For both these significations there is but one word in Latin; but in the Greek there is a distinct word for each, for the word "ethos" is written sometimes with a long, and sometimes a short "e".
Now "moral" virtue is so called from "mos" in the sense of a natural or quasi-natural inclination to do some particular action. And the other meaning of "mos," i.e. "custom," is akin to this: because custom becomes a second nature, and produces an inclination similar to a natural one. But it is evident that inclination to an action belongs properly to the appetitive power, whose function it is to move all the powers to their acts, as explained above (Question 9, Article 1). Therefore not every virtue is a moral virtue, but only those that are in the appetitive faculty.
Reply to Objection 1. This argument takes "mos" in the sense of "custom."
Reply to Objection 2. Every act of virtue can be done from choice: but no virtue makes us choose aright, save that which is in the appetitive part of the soul: for it has been stated above that choice is an act of the appetitive faculty (13, 1). Wherefore a habit of choosing, i.e. a habit which is the principle whereby we choose, is that habit alone which perfects the appetitive faculty: although the acts of other habits also may be a matter of choice.
Reply to Objection 3. "Nature is the principle of movement" (Phys. ii, text. 3). Now to move the faculties to act is the proper function of the appetitive power. Consequently to become as a second nature by consenting to the reason, is proper to those virtues which are in the appetitive faculty.
Source: Summa Theologica (New Advent)