| Quote #1
Shall I compare thee to a summer’s day?
At the start, we’re told that this will be a poem putting man and the natural world side by side for comparison, and apparently an attempt to favor man over the summer’s day. Let’s see how that develops:
| Quote #2
Thou art more lovely and more temperate:
At first glance, these lines look like the poet is bashing summer, in favor of "thee," who is "more lovely and more temperate." That’s true enough, as he’s definitely complaining about summer, but pay close attention to how he words these complaints. He says that winds "shake" "darling buds," that summer has a "lease," that heaven has an "eye," and that that eye, the sun, has a "complexion," which implies a face. What do all of those quoted words have in common? They’re all ways of describing humans or their actions. In other words, he can only describe nature by personifying it. This is especially pointed in the words "temperate" and "complexion," since they can both describe states of human health (at least as understood in Shakespeare’s time). If you had a good temperament and complexion, your internal humours, or various liquids, were in good proportions. So basically, even if nature is a little less lovely than a human, they clearly are made of the same things and subject to the same rules.
| Quote #3
And every fair from fair sometime declines,
Here the poet makes the similarities even more clear. He’s stopped trying to differentiate between man and nature at all, and instead points toward their universal similarity: they’re both slaves to time.