In "A Defence of Poetry,” Shelley suggests that thoughts and feelings in life are "always arising unforeseen and departing unbid
den.” Which lines from "Mutability” also reflect the idea that life is fleeting? We are as clouds that veil the midnight moon; How restlessly they speed, and gleam, and quiver Or like forgotten lyres, whose dissonant strings Give various response to each varying blast We rest.—A dream has power to poison sleep; We rise.—One wandering thought pollutes the day We feel, conceive or reason, laugh or weep; Embrace fond woe, or cast our cares away
In these lines, Shelley compares people to clouds that appear at night and veil the midnight moon. He states that these clouds "speed, gleam and quiver" restlessly. The metaphor is intended to reference human life. Just like the clouds, human life is brief. Therefore, these are the lines that best support the idea that life is fleeting.
