The major theoretical contributions of Kitzinger's later career are embodied in his book Byzantine art in the making (1977), originally delivered as a series of lectures at the University of Cambridge, and in a volume of his collected essays, The art of Byzantium and the medieval West (1976). In both volumes Kitzinger maintained his life-long preoccupation with the analysis of style change in late antique and early medieval art, and his conviction that stylistic analysis could speak with an authority equal to that of iconography or textual history. To this end he developed a theory of "modes," according to which certain styles were appropriate to the depiction of certain subjects. In Byzantine art in the making, furthermore, he essayed a bold attempt to trace the stylistic "dialectic" of the period in question: