Objection 1. It would seem that infused virtue does not differ in species from acquired virtue. Because acquired and infused virtues, according to what has been said (3), do not differ seemingly, save in relation to the last end. Now human habits and acts are specified, not by their last, but by their proximate end. Therefore the infused moral or intellectual virtue does not differ from the acquired virtue.
Objection 2. Further, habits are known by their acts. But the act of infused and acquired temperance is the same, viz. to moderate desires of touch. Therefore they do not differ in species.
Objection 3. Further, acquired and infused virtue differ as that which is wrought by God immediately, from that which is wrought by a creature. But the man whom God made, is of the same species as a man begotten naturally; and the eye which He gave to the man born blind, as one produced by the power of generation. Therefore it seems that acquired and infused virtue belong to the same species.
On the contrary, Any change introduced into the difference expressed in a definition involves a difference of species. But the definition of infused virtue contains the words, "which God works in us without us," as stated above (Question 55, Article 4). Therefore acquired virtue, to which these words cannot apply, is not of the same species as infused virtue.
I answer that, There is a twofold specific difference among habits. The first, as stated above (54, 2; 56, 2; 60, 1), is taken from the specific and formal aspects of their objects. Now the object of every virtue is a good considered as in that virtue's proper matter: thus the object of temperance is a good in respect of the pleasures connected with the concupiscence of touch. The formal aspect of this object is from reason which fixes the mean in these concupiscences: while the material element is something on the part of the concupiscences. Now it is evident that the mean that is appointed in such like concupiscences according to the rule of human reason, is seen under a different aspect from the mean which is fixed according to Divine rule. For instance, in the consumption of food, the mean fixed by human reason, is that food should not harm the health of the body, nor hinder the use of reason: whereas, according to the Divine rule, it behooves man to "chastise his body, and bring it into subjection" (1 Corinthians 9:27), by abstinence in food, drink and the like. It is therefore evident that infused and acquired temperance differ in species; and the same applies to the other virtues.
The other specific differences among habits is taken from the things to which they are directed: for a man's health and a horse's are not of the same species, on account of the difference between the natures to which their respective healths are directed. In the same sense, the Philosopher says (Polit. iii, 3) that citizens have diverse virtues according as they are well directed to diverse forms of government. In the same way, too, those infused moral virtues, whereby men behave well in respect of their being "fellow-citizens with the saints, and of the household [Douay: 'domestics'] of God" (Ephesians 2:19), differ from the acquired virtues, whereby man behaves well in respect of human affairs.
Reply to Objection 1. Infused and acquired virtue differ not only in relation to the ultimate end, but also in relation to their proper objects, as stated.
Reply to Objection 2. Both acquired and infused temperance moderate desires for pleasures of touch, but for different reasons, as stated: wherefore their respective acts are not identical.
Reply to Objection 3. God gave the man born blind an eye for the same act as the act for which other eyes are formed naturally: consequently it was of the same species. It would be the same if God wished to give a man miraculously virtues, such as those that are acquired by acts. But the case is not so in the question before us, as stated.
Source: Summa Theologica (New Advent)