Eden is the paradise of endless happiness and no violence, and the speaker spends most of the poem asking whether anywhere like it could really exist. The questions come one after another, short and unsure: "Will it exist, / Can it exist?" Then the doubt sharpens into a darker suggestion, that Eden might be "something made / Up" simply to comfort us.
The speaker doesn't seem certain either way. The poem leans toward doubt, but the last two lines change the tone. Calling Eden "a place that / Doesn't exist" sounds like a conclusion, yet the final words, "That I wish did," reveal longing underneath it. The speaker can't quite believe in paradise but can't stop wanting it.
The mood is quiet, wistful and a little sad. The short, broken lines make the poem feel like hesitant thinking aloud, and the line break after "made" leaves "Up" hanging alone, as if the idea of Eden is being cut down to size. It ends with hope that's honest but tired.