Objection 1. It would seem that shamefacedness is not about a disgraceful action. For the Philosopher says (Ethic. iv, 9) that "shamefacedness is fear of disgrace." Now sometimes those who do nothing wrong suffer ignominy, according to Psalm 67:8, "For thy sake I have borne reproach, shame hath covered my face." Therefore shamefacedness is not properly about a disgraceful action.
Objection 2. Further, nothing apparently is disgraceful but what is sinful. Yet man is ashamed of things that are not sins, for instance when he performs a menial occupation. Therefore it seems that shamefacedness is not properly about a disgraceful action.
Objection 3. Further, virtuous deeds are not disgraceful but most beautiful according to Ethic. i, 8. Yet sometimes people are ashamed to do virtuous deeds, according to Luke 9:26, "He that shall be ashamed of Me and My words, of him the Son of man shall be ashamed," etc. Therefore shamefacedness is not about a disgraceful action.
Objection 4. Further, if shamefacedness were properly about a disgraceful action, it would follow that the more disgraceful the action the more ashamed would one be. Yet sometimes a man is more ashamed of lesser sins, while he glories in those which are most grievous, according to Psalm 51:3, "Why dost thou glory in malice?" Therefore shamefacedness is not properly about a disgraceful action.
On the contrary, Damascene (De Fide Orth. ii, 15) and Gregory of Nyssa [Nemesius, (De Nat. Hom. xx)] say that "shamefacedness is fear of doing a disgraceful deed or of a disgraceful deed done."
I answer that, As stated above (I-II, 41, 2; I-II, 42, 3), when we were treating of the passions, fear is properly about an arduous evil, one, namely, that is difficult to avoid. Now disgrace is twofold. There is the disgrace inherent to vice, which consists in the deformity of a voluntary act: and this, properly speaking, has not the character of an arduous evil. For that which depends on the will alone does not appear to be arduous and above man's ability: wherefore it is not apprehended as fearful, and for this reason the Philosopher says (Rhet. ii, 5) that such evils are not a matter of fear.
The other kind of disgrace is penal so to speak, and it consists in the reproach that attaches to a person, just as the clarity of glory consists in a person being honored. And since this reproach has the character of an arduous evil, just as honor has the character of an arduous good, shamefacedness, which is fear of disgrace, regards first and foremost reproach or ignominy. And since reproach is properly due to vice, as honor is due to virtue, it follows that shamefacedness regards also the disgrace inherent to vice. Hence the Philosopher says (Rhet. ii, 5) that "a man is less ashamed of those defects which are not the result of any fault of his own."
Now shamefacedness regards fault in two ways. On one way a man refrains from vicious acts through fear of reproach: in another way a man while doing a disgraceful deed avoids the public eye through fear of reproach. In the former case, according to Gregory of Nyssa (Nemesius, De Nat. Hom. xx), we speak of a person "blushing," in the latter we say that he is "ashamed." Hence he says that "the man who is ashamed acts in secret, but he who blushes fears to be disgraced."
Reply to Objection 1. Shamefacedness properly regards disgrace as due to sin which is a voluntary defect. Hence the Philosopher says (Rhet. ii, 6) that "a man is more ashamed of those things of which he is the cause." Now the virtuous man despises the disgrace to which he is subject on account of virtue, because he does not deserve it; as the Philosopher says of the magnanimous (Ethic. iv, 3). Thus we find it said of the apostles (Acts 5:41) that "they (the apostles) went from the presence of the council, rejoicing that they were accounted worthy to suffer reproach for the name of Jesus." It is owing to imperfection of virtue that a man is sometimes ashamed of the reproaches which he suffers on account of virtue, since the more virtuous a man is, the more he despises external things, whether good or evil. Wherefore it is written (Isaiah 51:7): "Fear ye not the reproach of men."
Reply to Objection 2. As stated above (Question 63, Article 3), though honor is not really due save to virtue alone, yet it regards a certain excellence: and the same applies to reproach, for though it is properly due to sin alone, yet, at least in man's opinion, it regards any kind of defect. Hence a man is ashamed of poverty, disrepute, servitude, and the like.
Reply to Objection 3. Shamefacedness does not regard virtuous deeds as such. Yet it happens accidentally that a man is ashamed of them either because he looks upon them as vicious according to human opinion, or because he is afraid of being marked as presumptuous or hypocritical for doing virtuous deeds.
Reply to Objection 4. Sometimes more grievous sins are less shameful, either because they are less disgraceful, as spiritual sins in comparison with sins of the flesh, or because they connote a certain abundance of some temporal good; thus a man is more ashamed of cowardice than of daring, of theft than of robbery, on account of a semblance of power. The same applies to other sins.
Source: Summa Theologica (New Advent)