Beauty was once defined, by the medievals, as the "splendor of form." By this it was understood that a thing is seen to be beautiful the more its inner nature shines forth, presents itself with a kind of radiance to the beholder. The experience of beauty, then, is really an intense awareness of the form, or nature, of a thing, insofar as that nature strikes one by its radiance. Mere knowledge of the truth of a thing is nothing more than simply the awareness of its form; but the experience of its beauty is the awareness of the form as something which radiates, shines forth, even overwhelms the knower with its inner light. Beauty has everything to do with knowledge; the very word "splendor" indicates brilliance, intense visibility, and so intense intelligibility. To know the beautiful thus seems to involve the experience, not only of the visible thing, but of the very intensity of its visibility. The form of a beautiful thing is not simply there in the thing, but it is there in such a way that it loudly declares its presence and displays itself to the eye.
Form is a kind of actuality; it is in virtue of its actuality that form is the principle of intelligibility in things. Thus, in a prior sense, it is simply speaking actuality that is the principle of intelligibility in things. As we have seen in our earlier discussion, the measure of a thing's participation in actuality is the measure of its intelligibility. Sensible creatures participate in actuality in a twofold sense: by their form and by their being (esse). Beauty is defined as the "splendor of form." Could this not also be extended to include the "splendor of being"? -- because it is the splendor of actuality, the splendor of a thing's inner intelligibility? To be aware of the beauty of things is to be aware of their intense inner intelligibility, which is the intensity of their actuality, both form and being. It is thus almost necessary to have some sort of intuition of the participatory structure of beings - it may be an incommunicable intuition; in fact it usually is. It is also necessary to be aware of the intelligible content of things, in order to see their beauty: one must be intensely aware of what it is, and that it is. The experience of beauty cannot really be separated from this awareness.
(This makes me think that aesthetic experience and what I call "symbolic knowledge" - the knowledge of the symbolic meaning of things, through their forms - are very closely connected, perhaps inseparable. In describing the beauty of the world, one cannot neglect to attend to what the world is, and what is the nature of its parts, and their relation to each other, in detail.)
Beauty as a transcendental is not divorced from the particular beauty of things. Things are beautiful insofar as they are actual, and that actuality is splendorous. The degree of actuality in things differs, however, according to hierarchical order in the order of substances, as well as in the order of accidents. (I have a lot of thinking to do about accidental forms and participation, and symbolism in accidents...) Thus, things are beautiful according to the degree of their participation in what is fully actual: man by his substance is more beautiful than an animal, because he participates more perfectly in the actuality of form - his substance is more "taken over" by subsistent spirituality than any other cosmic substance, which falls short of true spirituality. But because man and the lower natural substances both participate in actuality in common, though in greater and lesser modes, beauty is something common to them all precisely inasmuch as actuality is common to them all. To this degree, beauty is a transcendental. All the more so in the sense that all things participate in actuality by having being (esse).
Another dimension of the experience of beauty might be the awareness of its very transcendence. In other words, an intense awareness of the participation of a particular thing in something much greater than itself, something universal, something that exerts its influence on a cosmic and even meta-cosmic scale. The more acutely one is aware of the actuality of a thing, the more one is aware of a nature or a meaning that extends far beyond the dimensions of this particular instance. Every particular holds a mystery, because by participation it brings into this finite moment and place an infinitesimal manifestation of something in itself unlimited. The ancients and the medievals loved to emphasize that in any whole, the perfection of the whole is greater than the perfection of the part. To see the part fully, then, was to see it not merely as an individual in its own right, but precisely as a part of something larger; and thus the larger meaning of the whole could be seen, in a contracted way, in the smallness of the part itself. In a paradoxical way, it is the individual perfection of the part that manifests the perfection of the whole, and yet in some sense the part seems to forget itself in that larger order, being transcended by a nobler and more universal perfection. The deepening of aesthetic experience - which is really a metaphysical experience, ultimately - relies on the vision of the multilayered actuality of things, their participatory structure, their ultimate reference to something that transcends them all individually. The soul of the beholder is opened up to what is the most universally beautiful, and ultimately to subsistent Beauty itself.