Question VII: On immodesty

TO Modesty this vice is opposed, and it consists in transgressing the due measure of those operations which require a mean beyond mediocrity in the senses, in food, dress, games, etc.

But as modesty shines forth especially in dress and outward ornament, in moderate studiousness, and in games not exceeding the bounds of Eutrapelia, so immodesty stands in the opposites, as St. Thomas teaches, quaest. cit.

FIRST, indeed, superfluity of ornament is a sin opposed to modesty in outward appearance by excess, namely when one uses unmeasured cultivation, whether in clothing or in other things, otherwise than is fitting: namely either by referring it to vainglory, or to illicit pleasure, or by giving it more careful attention than is proper; or when he directs his adornment to exciting to sin; or when fraud and falsehood are mixed into that cultivation, as St. Thomas discusses, art. 1. et 2. quaest. 169.

From these you have when they are mortal sins, namely when they are done with a mortal end, or cause grave sin.