Amiability

Amiability necessarily comes into the mix when we start talking about beauty.

Beauty here meaning not a natural gift such as Ava Gardner had but something that can be achieved by practicing certain virtues. Austen would insist that these virtues are feminine; meaning by this that the best place to see these virtues in action is among women and not that men aren't capable of them.

And she would insist that amiability is part of the story. Readers of Burke will know that he connected the beautiful with love; the beautiful is the thing that makes us love.

But let's ask a rude question, are there girls who are not capable of being pretty? Catherine Morland comes off initially as a borderline case:

“Catherine grows quite a good–looking girl — she is almost pretty today,” were words which caught her ears now and then; and how welcome were the sounds! To look almost pretty is an acquisition of higher delight to a girl who has been looking plain the first fifteen years of her life than a beauty from her cradle can ever receive.

But surely there are people who are incapable of even this.

Here I think Austen requires virtue from both ends. It is not just an achievement to be beautiful, it is an achievement to see it as well. And thus it is a moral failing in Darcy that he cannot see the beauty of the other girls at the first ball in Pride and Prejudice. We have to be amiable enough to see good in human beings generally.

To put it another way, if you walk into a room full of men and women and can find only one of them to be passably attractive, then you are a moral failure.