The Latin word for art, ars - the root ar can be translated with the terms "conjunction" or "union" (Gr.: ararisko, areté) - means "structure," "system." Authentic art must therefore have a structure, i.e., a structure in the sense of the God-given "order" in nature. Once an artistic work abandons this "natural structure," it loses its "natural beauty"; it loses the mysterious splendor, which is the reflection of the divine resting on all God's works.

Thus we call beautiful what "corresponds to the measure of our nature; movements which in their dimensions correspond to our senses."(11) "We call beautiful the things the sight of which causes delight.... In the knowledge of the beautiful desire is calmed."(12)
According to Augustine and Thomas, beauty is the splendor ordinis, the reflection of divine order, the lightening up of inner harmony.

Art finds its context in nature, which is determined by God and which in turn finds its highest expression in the well-ordered human nature, in which the sensual powers are subordinated to the higher spiritual powers of reason and will, which for their part are subordinated to divine law. "Whatever things are done according to art or reason, should be made to conform to those which are in accordance with nature, and are established by the Divine Reason."(13)
"Art is not concerned with a mere imitation of nature-then it would be inferior to anything in reality. Rather, in pondering nature, art brings forth its works from the very creation of God. It contemplates creation to become familiar with it, attempting to discover the spirit and reflection of the divine even in physical existence.
Art is as far removed from any exaggerated, entirely materialistic and inadequate realism as it is from a false idealism, which sacrifices nature on the altar of a self-seeking, arrogant imagination."(14)
In contrast to the graphic arts, music and language do not deal with visual but with acoustic forms, i.e., sound images, which correspond to the essence of our human nature and our elevated vocation to perfection. These forms are meant to respond to the Creator's offer of grace in singing the praise of his holiness: "Thou hast turned for me my mourning into dancing; thou hast loosed my sackcloth and girded me with gladness, that my soul may praise thee and not be silent. O LORD my God, I will give thanks to thee for ever."(15)