The sense of proportion appears first as an aesthetic faculty (visual, auditive and motor). Only afterwards it develops into logical skills and literary perception.
He who lacks it is unable to distinguish the essential from the accidental. But not only that. Instead of a sense of beauty, he develops the desire for ugliness, to such a degree, that not finding it, he will invent it.
Not that he loves ugliness, but the more he hates its, the more he is unable to not look directly into it. It may be a physical or moral ugliness, or even both.
I don’t remember who said it, but this kind of person is characterized by an intense hate against Evil without the corresponding love for the Good. Whoever said it, that’s meticulously correct.
There is no technique or method: the ONLY thing that develops the aesthetic capacity is the repeated experience of Beauty in one’s daily life.
Neither do I believe in any moral education except the repeated experience of Goodness.