The most famous summer comparison in English actually argues summer is not good enough
Sonnet 18 sounds like a gentle compliment, yet its logic is a demolition job. Shakespeare raises the idea of comparing his beloved to a summer day only to list everything wrong with summer: gusty, brief, sometimes scorching, often clouded. The beloved wins, and the poem claims credit for keeping them alive.
The opening question is really a setup. Having asked whether he should make the comparison, the speaker immediately rejects it: the person he loves is lovelier and more even-tempered than any summer's day. What follows reads like a grumble about the weather. Harsh winds rattle the May buds, the season's lease expires too soon, the sun blazes too hot or hides behind cloud.
The eighth line widens the complaint into a law of nature. Every beautiful thing eventually loses its beauty, whether through accident or through the ordinary unfolding of nature's course. Up to this point the poem is a meditation on decay, and the beloved seems no safer than a rose in August.
Then comes the turn, signalled by a single word: But. "But thy eternal summer shall not fade", the speaker insists, and death will never be able to boast of having the beloved in its shadow. The reason is the poem itself. Once the beloved lives in eternal lines, they grow alongside time rather than being eaten by it.
The couplet makes the boldest claim of all: "So long as men can breathe, or eyes can see, / So long lives this, and this gives life to thee." The word this means the sonnet. The immortality on offer depends on readers continuing to exist, which turns every new reading into part of the bargain. Shakespeare, who was baptised in Stratford-upon-Avon in 1564 and died in 1616, lost his son Hamnet at age 11, and few details of his private feelings survive. The poem he left, one of 154 sonnets, has so far kept its promise.
Source: Sonnet 18: Shall I compare thee to a summer's day?
