beauty is in the eye of the beholder
Different people have different views on what is beautiful; beauty is subjective.
He is referring to the relativity of "Beauty is in the eye of the beholder" an idea that became popular in the 18th cent.
noun
Someone who observes or beholds; an observer or spectator.
A fictional monster in roleplaying games, a floating orb of flesh with a large mouth and many eyes on stalks.