What is the theme in The Afterlife by Billy Collins?

Humor is a theme in the poem. Because literature, especially poetry, has traditionally dealt with serious subject matter in a serious manner, critics rarely consider light verse "great" poetry. Collins's poem uses humor, however, to make a serious point: human experience is malleable, and the unknown far outweighs the known. By caricaturing those who hold various beliefs about the afterlife, Collins shows just how silly trying to fathom the unknown can be.