(This entry is adapted from Robert Augros, “Beauty Visible and Divine” published in The Aquinas Review, Volume II, 2004)

The Definition of Beauty
Saint Thomas defines beauty in four simple words: id quod visum placet, [*] that which pleases merely by being seen. Visum names the part of beauty pertaining to knowledge, and placet, the part pertaining to its ability to gratify. The notions seeing and pleasing are appropriate for this definition because they are more known than beauty and together manifest its nature.Not just anything that causes pleasure when seen is an example of beauty. Id quod visum placet means, not that the pleasure merely happens to follow vision, but that the vision alone causes the pleasure. An art collector can enjoy looking at the Mona Lisa in a museum even if there is no possibility he will ever own it. Why do antique car enthusiasts attend auto shows if they can never own or drive any of the cars? It is because simply looking at a perfectly restored 1939 Rolls Royce Wraith is a delight. This is beauty. The contemplation that characterizes beauty is disinterested. Independence from utility distinguishes the beautiful from the good. Although beauty is a special kind of goodness, the two are distinct.
The Constituents of Beauty
Next we need to determine what it is in a beautiful thing that causes delight simply by being seen. Saint Thomas proposes three things: “Three items are required for beauty: first, integrity or perfection, for things that are lessened are ugly by this very fact; second, due proportion or harmony; and third, brilliance—thus, things that have a bright color are said to be beautiful.”[†]
Integrity means that the object lacks no part that belongs to its species, for anything deficient or mutilated is not beautiful. This is obvious in the human face where even as little as a missing tooth mars beauty, to say nothing of a missing eye. Baldness, especially in women, harms beauty because it is a lack of something due. Also implied in this first constituent is that the object has nothing in it contrary to its nature, such as a face with scars, tumors, or a rash. Other names for integrity are wholeness, completeness, and perfection.
The second constituent of beauty is due proportion or harmony, which requires that all the parts be of the appropriate size and shape in relation to each other. A sketch of an attractive human face can be rendered ugly by making the nose too big, the eyes too close together, or otherwise interfering with the delicate balance of due proportions. Due proportion of parts results in a pleasing shape, so that form is connected to this second constituent of beauty, as is balance.The third constituent of beauty is brilliance, with its equivalents or dependent notions of color, light, splendor, luster, and clarity. Color and clarity are critical to the beauty of diamonds, rubies, sapphires, and other gemstones. Clarity is a transparency through which light can travel unimpeded. What do we mean by a beautiful day? Certainly not one which is rainy or so foggy that one cannot see beyond twenty feet. To be beautiful a day must be bright, clear, and full of light.
Beauty as a Path to God
The painter, the biologist, the chemist, and the physicist all encounter the beauty of grass at different levels. Nature’s beauty is not skin-deep; it penetrates the marrow. In all natural things, living and nonliving, and at every level within each thing, from grassy plain to electron, proton, and neutron, beauty saturates nature. Such abundant beauty of so many kinds and at so many levels could never come from chance. Beauty is so abundant in nature, it cannot arise from chance; there must be some reason for it. But that reason must be open to alternatives, since there is no absolute necessity that animals, plants, and nonliving things exhibit beauty in the first place. Therefore, the beauty found in nature proceeds from a cause not bound by necessity and yet with a reason for acting. Such a cause is a mind. Therefore, a mind is responsible for the beauty of natural things. That mind, standing behind nature and directing it to beauty, all men call God. Thales of Miletus, the first of the Greek philosophers, said, “Of all things that are . . . the most beautiful is the universe, for it is God’s workmanship.”[‡] As the poets intimate and the philosophers demonstrate, the loveliness and charm of a gazelle or an orchid are stepping stones to the loftiest and most exalted beauty of nature’s Author.

[*] Summa Theologica, I, q. 39, a. 8. The text actually says, “pulchra enim dicuntur quae visa placent.”
[†] Summa Theologica, I, q. 39, a. 8, c. Trans. Vernon J. Bourke, The Pocket Aquinas, 263. My emphasis.
[‡] Quoted by Diogenes Laertius, Lives of Eminent Philosophers (Cambridge: Harvard University Press, 1925), I, 37.