The foundation and fountain-head of good composition is sound understanding. The Socratic writings will provide you with material, and if you look after the subject-matter the words will come readily enough. The man who has learnt duty to his country and his friends, the kind of love he should feel for a parent, a brother, and a guest, the obligations of a senator and a judge, and the qualities required in a general sent out to lead his armies in the field— such a man will certainly know the qualities that are appropriate to any of his characters. I would lay down that the experienced poet, as an imitative artist, should look to human life and character for his models, and from them derive a language that is true to life.

– from “On the Art of Poetry” by Horace, translated by TS Dorsch and found in the Penguin Classics edition, Classical Literary Criticism