I answer that, As stated above (Q. 141, A. 4; Q. 157, A. 3), temperance brings moderation into those things wherein it is most difficult to be moderate, namely the concupiscences of pleasures of touch. Now whenever there is a special virtue about some matter of very great moment, there must needs be another virtue about matters of lesser import: because the life of man requires to be regulated by the virtues with regard to everything: thus it was stated above (Q. 134, A. 3, ad 1), that while magnificence is about great expenditure, there is need in addition for liberality, which is concerned with ordinary expenditure. Hence there is need for a virtue to moderate other lesser matters where moderation is not so difficult. This virtue is called modesty, and is annexed to temperance as its principal.
Reply Obj. 1: When a name is common to many it is sometimes appropriated to those of the lowest rank; thus the common name of angel is appropriated to the lowest order of angels. In the same way, mode which is observed by all virtues in common, is specially appropriated to the virtue which prescribes the mode in the slightest things.
Reply Obj. 2: Some things need tempering on account of their strength, thus we temper strong wine. But moderation is necessary in all things: wherefore temperance is more concerned with strong passions, and modesty about weaker passions.
Reply Obj. 3: Modesty is to be taken there for the general moderation which is necessary in all virtues. _______________________
SECOND ARTICLE [II-II, Q. 160, Art. 2]
Whether Modesty Is Only About Outward Actions?
Objection 1: It would seem that modesty is only about outward actions. For the inward movements of the passions cannot be known to other persons. Yet the Apostle enjoins (Phil. 4:5): "Let your modesty be known to all men." Therefore modesty is only about outward actions.
Obj. 2: Further, the virtues that are about the passions are distinguished from justice which is about operations. Now modesty is seemingly one virtue. Therefore, if it be about outward works, it will not be concerned with inward passions.
Obj. 3: Further, no one same virtue is both about things pertaining to the appetite—which is proper to the moral virtues—and about things pertaining to knowledge—which is proper to the intellectual virtues—and again about things pertaining to the irascible and concupiscible faculties. Therefore, if modesty be one virtue, it cannot be about all these things.
On the contrary, In all these things it is necessary to observe the "mode" whence modesty takes its name. Therefore modesty is about all of them.