He considered transcendentalism a kind of philosophical idealism that held that the ultimate reality was spiritual and not material. He thought that experience was limited in telling us what things are in themselves or what to value. Emerson also referred to a Kantian notion of “ideas or imperative forms,” which made experience possible, and he ascribed to Immanuel Kant (1724–1804) the label “Transcendental Forms,” for these realities of the mind and spirit.