The poem compares the poet's beloved to a summer day; the beloved is, however, "more lovely and more temperate". Summer can be shaken by rough winds, and its heat may be excessive. The biggest problem with summer, however, is its fleeting nature; like all seasons, it will pass more or less soon, and the speaker does not wish his beloved's beauty to fade. His solution is stating that just as his beloved is "more lovely", his beauty will outlive summer thanks to the poet's verses. "So long lives this", says the poet, meaning the poem, the beloved's beauty will survive, and his "eternal summer shall not fade".
Although we as the readers see how furious and proud of their beliefs both factions are, we see that they are arguing over something that is the same thing. Similar to arguing whether zebras are white with black stripes or black with white stripes.
