Life isn't cut-and-dry; it's complicated. Kunitz shows that complexity by calling this poem "The Layers," which comes directly from lines 37-38: "Live in the layers, / not in the litter." Instead of using the whole line, "Live in the layers," as the title, Kunitz takes a more subtle approach. He's not telling us what to do, he's letting us experience "The Layers" for ourselves and pull our own meanings from the text.
Most things are not as they appear on the surface and the truth lies somewhere below.
Kunitz is tapping into these interior crevasses to broaden our perspectives on how life works and what's possible. Consciousness and memory are "in the layers," so to speak, and this poem dives right in.