Still in the parlor, Uncle Toby continues his attempt to redirect the conversation toward the armies at Flanders. Walter takes the bait, but then lapses into a state of physical confusion when he removes his hat with his right hand and then has to reach across with his left to remove the handkerchief from his right coat pocket. Tristram criticizes his father for not pausing to switch hands, but Walter has never been one to retract a decision once he has advanced it. Uncle Toby, in contrast to Tristram, waits through Walter's contortions with patience and goodwill. He "whistles Lillabullero," however, at his brother's argument that babies were more frequently damaged during birth before the advent of modern medical technology.
The next physical struggle comes with Dr. Slop's attempt to untie the knot in his medical bag. Obadiah knotted it up to prevent it from clattering during transport so that he could hear himself whistle. Tristram suggests that this knot, too, contributed to the flattening of his nose. Dr. Slop cuts his thumb with a penknife. He falls to cursing Obadiah, and Walter offers him the use of one of his ready-made curses. The curse he produces is actually a Catholic excommunication document, written by Ernulphus the Bishop. Dr. Slop hesitates at its vehemence, but then is persuaded to continue with the excommunication, inserting Obadiah's name wherever relevant. Tristram offers the opinion that we are all original when we swear, an argument contradictory to his father's hypothesis that every curse is originally derived from this one by Ernulphus.
Susannah appears, announcing that she has cut her arm, the midwife has fallen and bruised her hip, and the baby is still not delivered. She relays the midwife's request that Dr. Slop be called upstairs to assist. Dr. Slop, however, is sensitive about the fact that he has been subordinated to the midwife, and bristles at being summoned like a servant. He begins to speak disparagingly of the traditional methods of midwifery and its rude instruments of "fingers and thumbs." He concludes his statement, in what Tristram calls "a singular stroke of eloquence," with a flourish of the newly invented forceps, which he has finally liberated from the knotted bag. Unfortunately, he also accidentally produces the squirt, which is tangled with the forceps. This prompts Toby to ask, innocent of his own sexual innuendo, "are children brought into the world by a squirt?" Dr. Slop demonstrates the forceps on Toby, skinning his hands and knuckles in the process. In the delivery room, Dr. Slop and the midwife debate about whether it is the child's hip or head that is foremost. Slop remarks that the question is of no small consequence, suggesting that if the child is male, his genitalia may be in danger from the forceps.
"It is two hours and ten minutes...since Dr. Slop and Obadiah arrived," declares Walter, "but to my imagination it seems almost an age." He prepares to deliver a philosophical lecture on "Duration," only to be interrupted by Toby, who steals the gist of the argument out from under him: "'Tis owning, entirely, quoth my uncle Toby, to the succession of our ideas." After a moment of consternation, Walter launches into the lecture anyway. He and Toby bicker, and the speech is again cut short. Tristram, sarcastically, regrets what the world has lost in the unfinished lecture.
Walter and Toby fall asleep, the others are busy upstairs, and the author takes advantage of this quiet moment to write the Preface, which deals with Locke's remarks on wit and judgment. Tristram opposes Locke's ranking of judgment above wit, arguing instead that they go hand in hand, like the two knobs on the back of the chair. The brothers are then awakened by the squeaking of the hinge as Corporal Trim peeks into the room.
Trim informs the group that Dr. Slop is in the kitchen making a bridge, for which Toby expresses his heartfelt gratitude. Toby believes Slop is repairing the drawbridge, and Tristram digresses to tell the story of how Trim and Bridget broke the bridge during a romantic rendezvous at the fortifications. The confusion is cleared up when Trim announces that the bridge under construction is for the baby's nose, which has been crushed by the forceps.