Tristram pauses to compare writing a book to giving a party. He says that he has left six places for critics, since he knows they'll just get mad if he leaves them out. He even allows a critic to speak, but the critic just wonders how Toby could be so foolish.
Tristram asks if the critic has ever read Locke's Essay upon the Human Understanding. Locke says that people get confused for three reasons: (1) the senses are dull; (2) consequently objects don't make a strong impression; (3) they can't remember the impressions that do get made. To explain Locke, Tristram uses the metaphor of sealing wax.
And this isn't any sealing wax: it belongs to Dolly, the imaginary servant of the imaginary critic. Keeping those imaginary characters straight?
But Toby's problem is a little different—it's all about his words. They're tricky, particularly philosophical words such as "essence," the basic translation for Sterne's Greek here.