His most famous work was "The Civilization of the Renaissance in Italy", published in 1860; it was the most influential interpretation of the Italian Renaissance in the nineteenth century and is still widely read. According to John Lukacs, he was the first master of cultural history, which seeks to describe the spirit and the forms of expression of a particular age, a particular people, or a particular place. His innovative approach to historical research stressed the importance of art and its inestimable value as a primary source for the study of history. He was one of the first historians to rise above the narrow nineteenth-century notion that "history is past politics and politics current history.