A good poem is a contribution to reality. The world is never the same once a good poem has been added to it. A good poem helps to change the shape of the universe, helps to extend everyone's knowledge of himself and the world around him.

Thomas’s remark treats poetry not as ornament or private reverie but as an active force that alters what can be thought, felt, and perceived. Calling a poem a “contribution to reality” suggests that language can add to the world’s stock of meanings as tangibly as inventions or discoveries do. The claim that the universe’s “shape” changes is hyperbolic but purposeful: a successful poem reorganizes readers’ inner lives—memory, desire, moral attention—and thereby shifts the shared cultural world. The final emphasis on self-knowledge aligns poetry with a kind of experiential epistemology: poems extend understanding by intensifying perception and articulating what was previously inchoate.