expound upon a subject, dissert upon a subject, descant upon a subject, write upon a subject, touch upon a subject
treat a subject, treat a subject thoroughly, treat of a subject, take up a subject, ventilate a subject, discuss a subject, deal with a subject, go into a subject, go into a subject at length, canvass a subject, handle a subject, do justice to a subject. hold forth [oral dissertation], discourse, delve into.