Although we aren't told it quite yet, Tristram actually has brought his mother to the point of bearing him. But it is to be put off still. Uncle Toby's character is the next item on the author's agenda, and he launches into it by interrupting Toby's sentence. (That sentence will be completed 10 chapters later, in Book 2, Chapter 6.)
Again we have a reminder that the writer has his own thoughts — it is March 26, 1759 — and one of his thoughts is about his Aunt Dinah, a family scandal. The story of Aunt Dinah and the coachman serves to show the great difference between the brothers, Walter and Toby, and it shows Toby's extreme modesty.
Tristram analyzes his "digressive-progressive" technique, and his argument in its favor is clear and convincing: the digressions are really digressions, but the story goes on because, as he says, we continue to know more about Uncle Toby's character even though Tristram is ostensibly talking about something else.
His discussion of the way he has solved the problem is a piece of learned jargon; he is satirizing techniques, rules, and mechanical approaches to writing. But it is nonetheless true; his claim that the digressions work in much more closely than they seem to turns out to be so. The architecture of the whole labyrinth is very careful. The supposedly casual attitude he has to his forward development — he'll be writing the book for forty years — is just a typical Shandean joke; he knows where he's going, and he has a sense of proportion.
The character drawing goes on. The wound in Toby's groin starts his hobby, although what it is we don't know yet. An exposé of Toby's hobby will provide all the clues we need in order to understand his character, but the author must first give more background about the origin of the hobby. But before that, he must tell about something before that — in the next book.
