Objection 1. It would seem that the honest is not the same as the beautiful. For the aspect of honest is derived from the appetite, since the honest is "what is desirable for its own sake" [Cicero, De Invent. Rhet. ii, 53. But the beautiful regards rather the faculty of vision to which it is pleasing. Therefore the beautiful is not the same as the honest.
Objection 2. Further, beauty requires a certain clarity, which is characteristic of glory: whereas the honest regards honor. Since then honor and glory differ, as stated above (103, 1, ad 3), it seems also that the honest and the beautiful differ.
Objection 3. Further, honesty is the same as virtue, as stated above (Article 1). But a certain beauty is contrary to virtue, wherefore it is written (Ezekiel 16:15): "Trusting in thy beauty thou playest the harlot because of thy renown." Therefore the honest is not the same as the beautiful.
On the contrary, The Apostle says (1 Corinthians 12:23-24): "Those that are our uncomely [inhonesta] parts, have more abundant comeliness [honestatem], but our comely [honesta] parts have no need." Now by uncomely parts he means the baser members, and by comely parts the beautiful members. Therefore the honest and the beautiful are apparently the same.
I answer that, As may be gathered from the words of Dionysius (Div. Nom. iv), beauty or comeliness results from the concurrence of clarity and due proportion. For he states that God is said to be beautiful, as being "the cause of the harmony and clarity of the universe." Hence the beauty of the body consists in a man having his bodily limbs well proportioned, together with a certain clarity of color. On like manner spiritual beauty consists in a man's conduct or actions being well proportioned in respect of the spiritual clarity of reason. Now this is what is meant by honesty, which we have stated (1) to be the same as virtue; and it is virtue that moderates according to reason all that is connected with man. Wherefore "honesty is the same as spiritual beauty." Hence Augustine says (Q83, qu. 30): "By honesty I mean intelligible beauty, which we properly designate as spiritual," and further on he adds that "many things are beautiful to the eye, which it would be hardly proper to call honest."
Reply to Objection 1. The object that moves the appetite is an apprehended good. Now if a thing is perceived to be beautiful as soon as it is apprehended, it is taken to be something becoming and good. Hence Dionysius says (Div. Nom. iv) that "the beautiful and the good are beloved by all." Wherefore the honest, inasmuch as it implies spiritual beauty, is an object of desire, and for this reason Tully says (De Offic. i, 5): "Thou perceivest the form and the features, so to speak, of honesty; and were it to be seen with the eye, would, as Plato declares, arouse a wondrous love of wisdom."
Reply to Objection 2. As stated above (103, 1, ad 3), glory is the effect of honor: because through being honored or praised, a person acquires clarity in the eyes of others. Wherefore, just as the same thing makes a man honorable and glorious, so is the same thing honest and beautiful.
Reply to Objection 3. This argument applies to the beauty of the body: although it might be replied that to be proud of one's honesty is to play the harlot because of one's spiritual beauty, according to Ezekiel 28:17, "Thy heart was lifted up with thy beauty, thou hast lost thy wisdom in thy beauty."
Source: Summa Theologica (New Advent)