Tristram writes a chapter on sleep — apropos of the fact that everyone is asleep — and he sticks to the subject.
Walter asks Susannah to send "Trismegistus" down so that he and Toby can see him. The request touches off a general panic: Susannah confesses that the child has been named "Tristram," and Mrs. Shandy is in a "hysterick fit" about it. Walter calmly puts on his hat and goes out.
Tristram explains why his father went out to the fish pond with this latest affliction instead of taking it upstairs to the bed as before: first, it was different, and second, there is something about fish ponds.
Trim enters and tells Uncle Toby that "it" wasn't his fault — meaning the cow's breaking down the fortifications (first mentioned in Book 3, Chapter 38) — and Toby reassures him that it was the fault of Susannah and the curate — meaning the misnaming of Tristram. They agree that names don't mean very much in the long run, in the heat of battle: Trim would have fought as gallantly under his own name (James Butler) as he did under his nickname. They are acting out a valiant offensive when Walter reenters. He seats himself and begins his lamentation: everything has so far gone wrong for his child, but the name "Trismegistus" might have fixed it all: conception, infelicitous gestation period (because Mrs. Shandy "fumed inwardly" about not being able to go to London to have the baby), pressure on the skull by being born head first, crushed nose. Toby recommends sending for Parson Yorick.
Tristram considers the charge of a critic (his usual accuser) that he has trampled on many people with his horse (his hobby-horse, the book he is writing), even on a king. He denies it and tells the story of King Francis I of France. The king, hoping to make friends of the Swiss, offers them the honor of being godfather to his latest son; when they want to name the child "Shadrach, Mesech, and Abed-nego" — all three — the king demurs. Since there is no money in the royal treasury to buy them off and soothe their feelings, the king decides to go to war with them.
The author says that he is ashamed to ask the reader to take him seriously now after his "fanciful guise of careless disport," but seriously, he is not writing against King Francis I or against any of a host of other things. "If 'tis wrote against any thing, — 'tis wrote, an' please your worships, against the spleen," that is, against bad humor. His intention is to "drive the gall and other bitter juices from the gall bladder, liver, and sweet-bread of his majesty's subjects . . . down into their duodenums."
Although a chapter on sleep contributes nothing to the Shandy family story, it is valid from the point of view of the author himself: he is writing a book that contains "various things" besides Shandy history. The chapter is outside the Shandy history but inside the "Life and Opinions" framework.
The third accident is revealed to Walter as he discovers that there is no one in his house named "Trismegistus." The author skillfully varies the impact of this latest frustration; it is a grave blow to Walter, but he doesn't comment until several chapters later when he unburdens himself of his lamentation. In the meantime, we remain in suspense, wondering why he doesn't react immediately and what he will do when he does react.
Misunderstanding and faulty communication surge up still again when Trim and Toby discuss the "accident," Trim thinking of the cow and the fortifications, Toby, of the misnaming. We are reminded of the "bridge" of Book 3.
There is nothing but hobby-horses in Chapters 18 and 19: Trim and Toby are caught up by their enthusiasm about how one breaches a fortification, and Walter enters deep in thought about all the awful things that have destroyed the future of his child.
Should we take Tristram seriously when he says that the main purpose of his book is to amuse and cheer up the reader? We can easily believe him, but we should not limit our understanding of it to just that point; here he says only that he is writing against spleen. He is writing it for many other things. The difficulty lies in believing that anyone who can find humor in practically everything can ultimately have serious things to say as well. A serious manner — "gravity" — is "a mysterious carriage of the body to cover the defects of the mind," quotes Tristram earlier (Book 1, Chapter 11). Levity and humor, similarly, may be covering up something too — something other than "defects of the mind," of course.