The author ties together all the facts leading up to and including Uncle Toby's hobby: the setback in his getting well, the first idea for a map of Namur, the military books that fire his imagination, Trim's proposal for the scale models on the bowling green at Shandy Hall, and their setting off to start work. We know all there is to know about that part of Toby's character, and henceforth, when Toby sees everything in relation to that single ruling passion for fortifications, we understand perfectly.
Tristram's references to John Locke again remind us that the author was working in the context of eighteenth-century psychology, philosophy, and epistemology. Even though he cites Locke in order to show a contrary notion, he depends quite a bit on Locke.
The author's continuing close involvement with his characters and his insistence on his job as author is seen in the "spirited apostrophe" to his Uncle Toby and his beginning a fresh chapter. In Chapter 4, he remembers the interrupted sentence — although we may have forgotten it already — and at the end of Chapter 5 he tells us that later he will pick up what is digression (Toby's hobby) and make it a part of the main story. The suspension of the story of Toby's hobby is as calculated as the suspension of Toby's sentence.
Corporal Trim's character is also drawn by means of his hobbyhorse: "The fellow lov'd to advise, — or rather to hear himself talk. . . . Set his tongue a-going, — you had no hold of him." The proposal by Trim to build the models is a perfect demonstration of his oratory; he is involved with Uncle Toby in the fortifications, but that is merely a second-string hobby-horse for him.
