A phrase used to imply that beauty is not a qualifiable thing, that what one person considers beautiful may be ugly to another, and that no matter what you look like, or what anything looks like, to someone, it is beautiful.

It's true, to a point. Various studies and experiments have determined that physical attractiveness of a human being is not quite so subjective. There are factors that influence how attractive a person is to others.

Symmetry is a big one. The less symmetry in a face, the less attractive a person is. Everyone has some degree of symmetry, and some degree of asymmetry, but the more symmetry, the more attractive you are.

There are also certain ratios of distance and size, and they vary a little from male to female, but not a lot.

If you combine more than one face, to get a sort of hybrid of the two, the hybrid is likely to be more attractive than either person. And the more you blend together, the more attractive the face becomes. It's almost like the average face is the most attractive one. Average in feature size, distance, etc.

And there are features for the body also. So in a way, you can quantitatively determine how attractive you are. But of course, that only goes so far, as nobody (or almost nobody) cares only about the physical.