Lovers say extravagant things, and the speaker of Sonnet 104 opens with one of the boldest: to him, his "fair friend" can never grow old. The first line is plain and confident, built mostly from one-syllable words, like a vow. Then the poem sets about testing the vow and slowly lets it come apart. The friend is never named, and the poem needs no name. What matters is the speaker's stubborn belief and the doubt that creeps in beneath it.
The evidence he offers is oddly exact. Three years have passed since he first saw the friend, and he counts them through the seasons. "Three winters cold / Have from the forests shook three summers' pride": winter becomes a physical force that shakes the leaves from the trees, and "pride" makes summer's full foliage sound almost vain. Then "three beauteous springs to yellow autumn turn'd" and "three April perfumes in three hot Junes burn'd", where the scent of spring is scorched away by midsummer heat. The word "three" appears five times in five lines, as if the speaker were ticking off days on a wall. All this destruction happens in the natural world, while the friend, "fresh," stays untouched. The first eight lines build a confident contrast: the year turns and the friend does not.
The turn comes at line nine, with a sigh: "Ah!" The speaker now offers an image that quietly works against him. Beauty is like the hand of a clock or sundial, which "steal[s] from his figure, and no pace perceiv'd." The hand slips away from its numeral so gradually that nobody sees it move, and time becomes a thief who takes only a little at once. The friend's looks "methinks still doth stand," but "methinks" is a hedge, and the next line contradicts it: the beauty "Hath motion." The speaker admits that what he sees may not be what is true, and "mine eye may be deceiv'd."
That word "eye" links back to the second line's "first your eye I ey'd," where "eye," "I" and "ey'd" almost blur into one sound, as though looking and loving were the same act. By line twelve the speaker's eye has become unreliable. The poem is built on trust in his eyesight, and it ends by doubting it. The rhyme reinforces this. "Perceiv'd" and "deceiv'd" close lines ten and twelve, so the sound itself says that what we fail to notice is exactly what fools us.
The form supports this slow collapse. The poem follows the Shakespearean pattern of three quatrains and a couplet, rhymed abab cdcd efef gg, in iambic pentameter. The first two quatrains are steady and almost mechanical, one season after another. The third quatrain is shorter on certainty and fuller of qualifications. The couplet then changes the audience: "hear this thou age unbred," the speaker says, addressing the unborn future. His message is blunt: "Ere you were born was beauty's summer dead." The inverted word order delays "dead" to the very end of the poem. One way to read it is that future generations will arrive too late to see this beauty, because its summer will already be over. The speaker began with a private claim, "To me," and finishes by speaking to all the years to come, as a witness.
That is what makes the sonnet worth reading. Some poems in the sequence hope that verse might outlast time, but this one is more honest and more unsettled. It shows a person who knows the truth about time and still half-believes his own eyes. The ending does not rescue the friend from age. It records that something beautiful existed and was seen, and that the seeing was real even if it could not last. The couplet's finality has its own sadness, because the poem begins by saying the friend cannot grow old and ends with the word "dead."