The title gives the poem its key: a solipsist is someone who feels that only their own mind is truly real, and the poem reads like a portrait of that isolation. The speaker begins by admitting a pull toward madness, comparing it to a verse they can never quite understand. That's a nice twist, because it suggests madness is both attractive and out of reach, something they keep circling without ever grasping.
The next lines turn darker and stranger. The speaker expects every child to be "gone to be born," as if life is always already leaving or slipping away before it arrives. Then comes a sense of abandonment: the speaker is a "ward of a poisoned well," cared for by something that can only harm. The final image, prayers lying in "an indifferent box," feels cold and final. Nobody answers. The mood is bleak, withdrawn, and quietly hopeless, with a speaker sealed inside their own head.