Objection 1. It would seem that honesty should not be reckoned a part of temperance. For it is not possible for a thing to be part and whole in respect of one same thing. Now "temperance is a part of honesty," according to Tully (De Invent. Rhet. ii, 53). Therefore honesty is not a part of temperance.
Objection 2. Further, it is stated (3 Esdra 3:21) that "wine... makes all thoughts honest." But the use of wine, especially in excess, in which sense the passage quoted should seemingly be taken, pertains to intemperance rather than to temperance. Therefore honesty is not a part of temperance.
Objection 3. Further, the honest is that which is deserving of honor. Now "it is the just and the brave who receive most honor," according to the Philosopher (Rhet. i, 9). Therefore honesty pertains, not to temperance, but rather to justice and fortitude: wherefore Eleazar said as related in 2 Maccabees 6:28: "I suffer an honorable [honesta] death, for the most venerable and most holy laws."
On the contrary, Macrobius [In Somn. Scip. i] reckons honesty a part of temperance, and Ambrose (De Offic. i, 43) ascribes honesty as pertaining especially to temperance.
I answer that, As stated above (Article 2), honesty is a kind of spiritual beauty. Now the disgraceful is opposed to the beautiful: and opposites are most manifest of one another. Wherefore seemingly honesty belongs especially to temperance, since the latter repels that which is most disgraceful and unbecoming to man, namely animal lusts. Hence by its very name temperance is most significative of the good of reason to which it belongs to moderate and temper evil desires. Accordingly honesty, as being ascribed for a special reason to temperance, is reckoned as a part thereof, not as a subjective part, nor as an annexed virtue, but as an integral part or condition attaching thereto.
Reply to Objection 1. Temperance is accounted a subjective part of honesty taken in a wide sense: it is not thus that the latter is reckoned a part of temperance.
Reply to Objection 2. When a man is intoxicated, "the wine makes his thoughts honest" according to his own reckoning because he deems himself great and deserving of honor [Cf. 148, 6.]
Reply to Objection 3. Greater honor is due to justice and fortitude than to temperance, because they excel in the point of a greater good: yet greater honor is due to temperance, because the vices which it holds in check are the most deserving of reproach, as stated above. Thus honesty is more to be ascribed to temperance according to the rule given by the Apostle (1 Corinthians 12:23) when he says that "our uncomely parts have more abundant comeliness," which, namely, destroys whatever is uncomely.
Source: Summa Theologica (New Advent)