Non omnis virtus dicitur moralis, sed solum illa quae est in vi appetitiva, quia omnis actus virtutis potest ex electione agi, sed electionem rectam agit sola virtus quae est in appetitiva parte animae, dictum est enim supra quod eligere est actus appetitivae partis.
Not every virtue is a moral virtue, but only those that are in the appetitive faculty, because 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 (q13 a1).
Ad huius evidentiam, considerare oportet quid sit mos, sic enim scire poterimus quid sit moralis virtus. Mos autem duo significat. Quandoque enim significat consuetudinem, sicut dicitur Act. XV, "nisi circumcidamini secundum morem Moysi, non poteritis salvi fieri".
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."
Quandoque vero significat inclinationem quandam naturalem, vel quasi naturalem, ad aliquid agendum, unde etiam et brutorum animalium dicuntur aliqui mores; unde dicitur II Machab. XI, quod "leonum more irruentes in hostes, prostraverunt eos". Et sic accipitur mos in Psalmo LXVII, ubi dicitur, "qui habitare facit unius moris in domo".
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."
Et hae quidem duae significationes in nullo distinguuntur, apud Latinos, quantum ad vocem. In Graeco autem distinguuntur, nam ethos, quod apud nos morem significat, quandoque habet primam longam, et scribitur per eta, Graecam litteram; quandoque habet primam correptam, et scribitur per epsilon.
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".
Dicitur autem virtus moralis a more, secundum quod mos significat quandam inclinationem naturalem, vel quasi naturalem, ad aliquid agendum. Et huic significationi moris propinqua est alia significatio, qua significat consuetudinem, nam consuetudo quodammodo vertitur in naturam, et facit inclinationem similem naturali.
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.
Manifestum est autem quod inclinatio ad actum proprie convenit appetitivae virtuti, cuius est movere omnes potentias ad agendum, ut ex supradictis patet.
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 (q9 a1).