What single idea is developed throughout "sonnet 43"?

Sonnet 43 is a love poem in the form of a sonnet. A sonnet is a 14-line poem with a specifc rhyme scheme and meter (usually iambic pentameter). This poetry format-which forces the poet to wrap his thoughts in a small, neat package-originated in Sicily, Italy, in the 13th Century with the sonnetto (meaning little song), which could be read or sung to the accompaniment of a lute.

Sonnet 43 is a love poem of a or from a sonnet