In letters to Mrs. Ernest Benzon and Mrs. Thomas FitzGerald, Browning claims affinity with the great philosopher of the Will, Schopenhauer, and asserts that elements of vitalism are the “substratum” of his life and work. These letters confirm the poet's place in the line of vitalist thought shaped by Schopenhauer, the English Romantics, and Carlyle and further developed by Nietzsche, George Bernard Shaw, Henri Bergson, and D. H. Lawrence. Vitalism resists precise definition; each theorist advances a singular terminology and application. Schopenhauer's vitalism may be understood from his concept of cosmic Will; Carlyle's from the essential presence of energy, movement, and change in the world. Bergson used the term élan vital and Lawrence such characteristically vague phrases as “sense of truth” and “supreme impulse” to express faith in forces operating beneath or hovering above the surface of life. Broadly put, when a rational orientation to the world ceased to be adequate, when rationalism devolved into a falsification of reality's authentic energy, major vitalists came into existence and posited as the true reality a primitive, universal force of which everything in that reality is an objectification. Unlike other vitalists in the English tradition, such as Blake and Lawrence, Browning was not comfortable with cosmic images. His vitalism breaks from the main line to focus on the individual human will, which he saw as an intuitive impulse and as a means to realize the self and locate its place in the world. For Browning, the comprehension of life's vital movement lay in the dynamic energy of willed action.