“For beauty includes three conditions, ‘integrity’ or ‘perfection,’ since those things which are impaired are by the very fact ugly; due ‘proportion’ or ‘harmony’; and lastly, ‘brightness’ or ‘clarity,’ whence things are called beautiful which have a bright color.”
Thoughts: Art in churches represent God. They often contain images depicting God’s beauty and goodness. Because they reflect Truth, they are beautiful. Even things like ornate architecture are beautiful because they reflect perfection in craftsmanship and skill. Perfection reflects God so in this way even architecture is beautiful.
Excerpt from Summa Theologica, Part I, Question 39, Eighth Article, I answer that