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 (Philippians 4:5): "Let your modesty be known to all men." Therefore modesty is only about outward actions.
Objection 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.
Objection 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.
I answer that, As stated above (Article 1), modesty differs from temperance, in that temperance moderates those matters where restraint is most difficult, while modesty moderates those that present less difficulty. Authorities seem to have had various opinions about modesty. For wherever they found a special kind of good or a special difficulty of moderation, they withdrew it from the province of modesty, which they confined to lesser matters. Now it is clear to all that the restraint of pleasures of touch presents a special difficulty: wherefore all distinguished temperance from modesty.
In addition to this, moreover, Tully (De Invent. Rhet. ii, 54) considered that there was a special kind of good in the moderation of punishment; wherefore he severed clemency also from modesty, and held modesty to be about the remaining ordinary matters that require moderation. These seemingly are of four kinds. one is the movement of the mind towards some excellence, and this is moderated by "humility." The second is the desire of things pertaining to knowledge, and this is moderated by "studiousness" which is opposed to curiosity. The third regards bodily movements and actions, which require to be done becomingly and honestly [Cf. 145, 1], whether we act seriously or in play. The fourth regards outward show, for instance in dress and the like.
To some of these matters, however, other authorities appointed certain special virtues: thus Andronicus [De Affectibus] mentions "meekness, simplicity, humility," and other kindred virtues, of which we have spoken above (143); while Aristotle (Ethic. ii, 7) assigned eutrapelia to pleasures in games, as stated above (I-II, 60, 5). All these are comprised under modesty as understood by Tully; and in this way modesty regards not only outward but also inward actions.
Reply to Objection 1. The Apostle speaks of modesty as regarding externals. Nevertheless the moderation of the inner man may be shown by certain outward signs.
Reply to Objection 2. Various virtues assigned by various authorities are comprised under modesty. Wherefore nothing prevents modesty from regarding matters which require different virtues. Yet there is not so great a difference between the various parts of modesty, as there is between justice, which is about operations, and temperance, which is about passions, because in actions and passions that present no great difficulty on the part of the matter, but only on the part of moderation, there is but one virtue, one namely for each kind of moderation.
Wherefore the Reply to the Third Objection also is clear.
Source: Summa Theologica (New Advent)