From instructor to associate Professor of English, University of Pennsylvania, 1924-1942, professor and graduate chairman, 1942-1947. Professor of English and comparative literature Columbia, 1947-1952. Professor Harvard, 1952-1960, Cabot Professor of English literature, 1960-1970, emeritus, 1970-1976.
Guggenheim fellow, 1953-1954, 65-66. Delaware Shakespeare Conference England, 1947. Alexander lecturer U. Toronto, 1954-1955.
British Academy Shakespeare lecturer, 1969.