Shelley's lines begin as a plea and quietly turn into an accusation. The speaker begs the person he loves to look at him and speak to him, but in the middle of the begging he admits what the looking and speaking really amount to. The addressee is left as a blank, since the title is just "To --", so the poem feels overheard, as if we have walked in on one side of a private quarrel. Its central idea is that love can become a closed circuit. The speaker pours out devotion, the beloved receives it, and nothing real passes between them.
The mirror is the key image. In the opening lines the speaker says her eyes "feed upon the love within mine own," then adds that this love "is indeed but the reflected ray / Of thine own beauty from my spirit thrown." His feeling is not independent of her. It is her beauty bounced back off him, like light off a surface. Four lines later the poem makes the point explicit, describing her as "one before a mirror, without care / Of aught but thine own features, imaged there." The cruel twist is that the mirror is the speaker himself. Even when she looks into his eyes, she is looking at herself. The image also suggests the myth of Narcissus, though the poem never names it.
Sound works the same way as sight. Her voice is "the tone / Of my heart's echo," so even her speech seems to return his own feelings to him. Mirror and echo are both ways of sending something back unchanged, and Shelley uses one for the eyes and one for the ears. Notice, too, how hesitant the speaker is: "I think I hear / That thou yet lovest me." He is not sure he is hearing love at all, and may only be hearing what he wants to hear.
The small word "yet" carries a lot of the poem's feeling. It opens the first line and the fifth, it appears twice in the seventh, and it begins the second stanza again with "And yet I wear out life in watching thee." Each time it shifts slightly. At first it means "all the same," as in "despite everything, look at me." Then it means "still," as in "you still love me." The repetition gives the poem a stubborn, circling rhythm, like someone who keeps making concessions and then insisting anyway. "Thine own" and "mine own" repeat too, and the ownership they insist on emphasizes how separate the two people are.
The form shapes this feeling. The first nine lines rhyme ababbcbcc, the same pattern as a Spenserian stanza, though here the last line is not stretched into a longer one and stays in the ten-syllable iambic line of the rest. The rhymes keep returning to the same sounds: "own," "thrown," "tone," and "alone" all chime, so the "b" rhyme circles through the stanza. That repetition fits a speaker who feels trapped going around in circles. The stanza also tends to run over the line breaks. "Alone" ends a line, but the sentence carries straight on into the simile of the mirror, so the loneliness is described just as the rhyme lands on it. The commands, "look on me" and "speak to me," are set off by dashes, which gives them an urgent, interrupted quality.
The last three lines shift from reproach to weary tenderness. "I wear out life in watching thee" plays on two meanings of "watching," since it can mean gazing at her and also keeping a long vigil over her. "Wear out" suggests slow erosion. Then comes the oxymoron "a toil so sweet at times," which sums up the whole relationship in four words. She is "kind when I am sick, and pity me," but pity is a much smaller thing than the love he asked for, and the speaker seems to know it. As given here, the poem breaks off on an ellipsis, in the middle of that thought, and the unfinished ending suits a feeling that never quite resolves.
What makes the poem worth reading is how it turns a familiar situation inside out. A love lyric usually praises the beloved. Here the speaker's love is made of her beauty, and the one thing he cannot give her is a self she is not already looking at. He is clear-sighted about his own devotion and unable to stop, which gives the poem its mixture of ache and irony.