Poetry is a phantom script telling how rainbows are made and why they go away.

Sandburg’s image treats poetry as an insubstantial but suggestive “script”: not a manual of facts, but a ghostly set of signs that intimates how beauty comes into being (“how rainbows are made”) and why it cannot be held (“why they go away”). The line frames poetry as a way of knowing that is indirect, intuitive, and transient—closer to wonder than explanation. It also implies that poetry’s subject is often the evanescent: moments of radiance, feeling, and meaning that appear briefly and then vanish. In that sense, the quote defends poetry’s value precisely in what science or plain statement cannot fully capture: the felt experience of emergence and loss.