Beauty is not limited to the arts (indeed, art is not always beautiful, but that's another topic). This set me to thinking about the many sorts of things that we humans can call beautiful:
And these are still quite general: it's not all of mathematics that we consider beautiful, but certain equations (e.g., Euler's equation and Maxwell's equations); in baseball, a well-turned double play can be a thing of beauty, but a routine fly ball not so much; and so on.
Furthermore, these beautiful things exhibit a wide range of attractive qualities, such as: fluidity, simplicity, intricacy, purity, polish, smoothness, sleekness, elegance, proportion, symmetry, asymmetry, line, composition, arrangement, form, structure, solidity, color, tone, rhythm, harmony, aliveness, permanence, evanescence, transcendence, earthiness, spontaneity, precision, virtuosity, imagination. It's not a mistake that some of these qualities are - or at least seem to be - at odds with each other. For instance, we might value precision and virtuosity in a musical performance, but if it's too precise it might start to feel robotic. Similarly, criteria of beauty can vary across times and cultures; as one example, in some East Asian cultures people rate symmetry less highly than people did in classical Greece.
The endless variety and particularity of beautiful things might make theoretical speculation more difficult, but they also give us so much celebrate and explore in the natural and human worlds.
(Cross-posted at Beautiful Wisdom.)