Man’s yesterday may ne’er be like his morrow;
Nought may endure but Mutability.

These lines assert that human life is defined by continual change: what one is or experiences “yesterday” will not reliably resemble “tomorrow.” The archaic “ne’er” and “nought” give the sentiment a proverbial, almost aphoristic force, while the capitalized “Mutability” personifies change as a governing law. In Shelley’s Romantic worldview, this can be read both as a sober recognition of instability—of fortunes, feelings, and social conditions—and as a critique of any claim to permanence (political, moral, or personal). The paradox “nothing endures but change” emphasizes impermanence as the only constant, inviting humility and adaptability in the face of time.