Consonne d’appui is a French term for “perfect rhyme”—that is, words like “pain” and “pane” that sound the same. In French poetry, it’s perfectly normal to have rhymed words that sound the same, but in English poetry this isn’t generally done (consonnes d’appui tend to strike English speakers as odd). As an English speaking poet, Shade would be expected to grimace at a consonne d’appui, but he loves them—and here he has a metaphysical theory as to why. To him, two unrelated words happening to sound the same is akin to the kinds of coincidences that show that the universe itself is planned and beautiful (“richly rhymed”). It’s actually through poetry itself that Shade can catch a glimpse of how he thinks the universe works—the way that he designs his poetry to be patterned and rhyming must resemble the way that the “players” design the universe. If people could decode the mysteries of the universe, they would find in it something similar to poetry—a sense that everything is orderly and beautiful, that the universe itself has been written in meter and rhyme. Shade takes great comfort in this insight—it suggests to him that his belief that his daughter still exists somewhere is no more absurd than his belief that he’ll wake up tomorrow, the 22nd of July. Of course, Shade does
not wake up the next morning, since he dies right after writing these lines. Just like the mountain/fountain incident, it’s possible to interpret this as a grim and cynical indication that Shade’s theories of the afterlife are false, but it’s also possible to explain this line about waking up the next day as another uncanny and possibly prophetic aspect of Shade’s poem that suggests that he is, in some small way, in tune with aspects of the universe beyond himself.