Answer:
"Nought may endure but Mutability."
Step-by-step explanation:
P.B. Shelley's "Defense of Poetry" is an essay that talks of how poets and poetry are the only things that enables humans to have the enjoyment that no one can provide. In an age of developed science and technology, Shelley argues that it is up to poets and writers to provide beauty and imagination to the world, which scientists and other 'experts' are unable to do so.
In his essay, Shelley presents an argument that despite all that is in the world, change is the only thing that lasts. And it is through the works of poets that this change is evident and enjoyed. Likewise, his poem "Mutability" contains the line "Nought may endure but Mutability" which reflects his argument that change is the only thing that lasts.