Obviously, words can describe the shape of a natural bridge; they can describe the shape of a monster. But they cannot describe the shape of the soul, changeable yet persistent, overwhelming but subtle. Feelings, Shelley and Jefferson agree, render words puny and inadequate. So yes, Shelley can tell you about feelings and their physiological manifestations, as can Jefferson, but neither can tell you the feeling itself.
At the turn of the nineteenth century, English speakers discovered that the word, the work of humanity, the fashioning of significance to sound, could not be conflated with reality. The name of the soul was not the soul, despite John and his Gospel. The discovery of the psyche coincided with the discovery of humanity’s powerlessness to control the universe by naming it, as Adam did in the Garden of Eden, or for people to understand their feelings by naming them. Mary Shelley could describe neither Frankenstein nor his monster, and the failure was magnificent.