"Mutability" begins with images of natural decay: "dissolution" moves over all human accomplishments, making "awful notes whose concord shall not fail, a musical but melancholy chime." Wordsworth's first hint of Romantic transcendence is in the picture of destructive time having a "concord," a metaphorical agreement, with nature. Only the pure in nature, who "meddle not with crime," hear dissolution's melody, so they are transcendent as well; their imaginations allow them to hear and realize that the decay of humanity is unalterable. Time cannot be appeased, but the imagination can accept its destructive march.
Wordsworth enlarges his transcendent imagery by giving the poem one solid, unchanging reality: "Truth fails not." Truth's "outward forms ... do melt like frosty rime" and "whitened hill and plain is no more," so the masks of truth are cast aside and lost. However, truth, like the Romantic imagination, continues on in forms that may be unrecognizable. A "tower sublime of yesterday" is gone, but the truth the tower represented remains. Wordsworth mentions almost casually that the tower is easily breached; a "casual shout" shatters it. However, truth is still standing, an image of transcendent durability.
Christianity was revived with the Romantic movement; inevitably, Wordsworth invokes Biblical references. The collapsed tower "royally did wear his crown of weeds," an unmistakable allusion to Christ's crown of thorns; the juxtaposition of "crown" and "weeds" gives a royal touch to unspoiled nature, the Romantic poets' true place of revelation. Wordsworth seems to be assuring the reader that truth will remain on its natural throne, and its disappearance into melted snow is only temporary as it awaits resurrection. Perhaps the "casual shout" that obliterates its earthly shell is the last trumpet.
Mutability means change, and Wordsworth's poem is solidly in the camp of Romantic transcendence -- change that evolves and deifies -- with its images of natural corruption, its Biblical allusions and its solid metaphor of nature and time's agreement. In a sense, the poem is also a romantic paradox: it foreshadows change but also prophecies the endurance of truth; it speaks of the imagination's apocalypse but also promises its resurrection.