How many people do not remember a glorious summer day that perfectly matched their inner mood? Sonnet 18 recalls this memory to people. And, is not this perfection of love not an appropriate way to describe one's sincere and lasting love by saying it is better than a summer's day? "Thou art more lovely and more temperate" is the quintessential compliment.
This sonnet is a love poem, like so many of Shakespeare's sonnets. In this one, the person to whom it is addressed is described in terms as beautiful as a summer's day. She is lovelier, actually, since the wind of summer's days rough the darling buds of May and the sun is too hot sometimes. Her beauty will not ever fade...not even in death...since as long as the lines Shakespeare are read she will live also.
Sonnet 18, Shakespeare's best known sonnet, describes beauty and decay, and references nature and someone beloved, making a comparison between both. What's significant about this sonnet is the self-reference -- although beauty decays as a person gets older and dies or as the seasons change from spring to winter, the couplet suggests that as long as this sonnet continues to be read, the beauty it describes will endure, like an eternal summer. (see Robert Frost's "Noting Gold Can Stay" for a more recent poem describing something similar.)
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