Shelley never quite says what he is talking about. The first line offers "one word", the second sets it aside ("For me to profane it"), and when "love" finally turns up in the ninth line, it is held at arm's length: "what men call love". The poem tiptoes around a feeling the speaker believes has been spoiled by overuse. Even the title joins in. "To --" leaves the addressee as a blank, just as the opening leaves the word unspoken.
The central idea is that the deepest feeling cannot be offered in ordinary terms, so it has to be offered in other ones. The speaker is not asking to be loved back. Judging by the poem, he asks only that his devotion be accepted, and that "pity from thee" be allowed to stand in for more. The shift from the everyday word to the language of "worship" turns a lover's request into something closer to a prayer.
The first stanza is built on a repeated pattern: "too ... for ... to ...". The word is "too often profaned / For me to profane it". The feeling is "too falsely disdained / For thee to disdain it". Then comes the twist: "One hope is too like despair / For prudence to smother". Prudence, personified, is pictured holding a pillow over a feeling that will not stop breathing, and the hope that resembles despair is a small paradox in itself. The pattern then breaks. The last two lines drop the tight "too ... for" logic for a plain comparison, pity "more dear / Than that from another". After three confident, balanced statements, the voice becomes quiet and exposed.
The sound supports this. Both stanzas rhyme ABAB CDCD, and the lines alternate between three beats and two. The long lines have a lilting, almost singing movement, and the short ones fall away on soft endings: "profane it", "smother", "another". Some rhymes are made from one word in two forms, as in profaned/profane and disdained/disdain, so the poem seems to circle a single point. In the second stanza, "accept not" and "reject not" end on the word "not", which puts refusal at the point where the voice trails off. Even the inverted "I can give not" sounds like a man stepping backwards while he asks.
That second stanza turns from statement to a single long question, and its vocabulary becomes religious: "worship", "Heavens", "devotion". "Profaned" in the first stanza already belonged to this world, since to profane is to treat something sacred as common. The speaker moves his feeling out of the marketplace of "what men call love" and into a temple. There is some boldness here, too. He claims that the Heavens "reject not" what he offers, bringing in a higher authority on his side.
The imagery stretches outward in three steps. First comes "the moth for the star". A moth usually flies at a flame and burns. A star is so far away that nothing can be burned, so this is desire with no possession in it and no harm done. Next, "the night for the morrow" widens the view to the whole sky and the slow turn towards daylight. Last, the picture dissolves into "something afar", which is as unnamed as the "one word" of the opening. The final phrase, "the sphere of our sorrow", can suggest both the earth we live on and the heavenly spheres we look up to. Sorrow is where we stand, and devotion is the thing that points out of it.
The poem is significant because it enacts what it describes. It is sixteen short lines about the worth of restraint, and it practises that restraint, hardly using its central word and stopping before it can overstate. The moth and the star give the idea its most memorable form, and they fit the Romantic habit of aiming feeling at something just out of reach. The poem also leaves a quiet question. The speaker says he cannot give "love", but what he offers instead, a devotion the Heavens would not turn away, may be a bigger claim than the one he gave up.