What is "The Sacred," anyway? A talisman? A hood ornament? Dancing? Driving? Praying? Poem-ing? It's hard to pin something abstract down, but this poem does a pretty good job.
Let's start with the Cadillac of all poetry titles. Calling a poem "The Sacred" is like saying "The Truth." Dunn is dealing with some big ideas and a lot of trunk space, and he wants a big title to fit the big theme. However, the poem addresses the subject matter in a down to earth, conversational way, so the super-intense title works by setting up an expectation of a seriously highbrow, religious poem.
But those expectations are upset when we start reading about a high school classroom discussion that turns into a description of driving around alone in a car. The juxtaposition of day-to-day experience mixed together with the idea of sacredness is reinforced by the important-sounding title mixed with the poem's content. That's Dunn's style, and this whopper of a title sets us up for the surprising insight that Dunn's simple words and seemingly simple content offer us.