Life is a jest; and all things show it.
I thought so once; but now I know it.

In two brisk rhyming lines, the speaker moves from suspicion to certainty: what once seemed a cynical hunch (“I thought so once”) has hardened into lived knowledge (“but now I know it”). Calling life “a jest” suggests not simple cheerfulness but a satiric, disillusioned view that human plans, pretensions, and moral posturing are repeatedly undercut by circumstance. The force of “all things show it” is cumulative—everyday experience becomes evidence that the world is structured like comedy or farce, where outcomes mock intentions. In John Gay’s literary world, such a sentiment aligns with Augustan satire’s habit of exposing social vanity and the gap between appearance and reality.