"Shall I compare thee to a summer's day?..."
See in text (Sonnet 18)
Shakespeare uses the question that begins this sonnet to challenge and question Petrarchan tropes. Petrarchan sonnets generally compare each part of the beloved’s body to a larger concept or natural system. This trope, called the blazon tradition, was used to describe the beloved as the most beautiful, or perfect embodiment of beauty. The speaker uses the question here to reject this trope: he will not compare his beloved to a summer’s day because the beloved is more lovely and more temperate.
The beginning of this sonnet plays on the proverb “as good as one shall see in a summer’s day,” meaning “as good as the best there is.” The speaker is essentially asking, shall I compare you to the best of the best?