Born in Estonia in 1901, Louis Isidore Kahn was to become one of the United States' most important architects of the post-war period, alongside the Modern masters Mies van der Rohe, Walter Gropius and Le Corbusier. Although renowned for a number of seminal modern works, he came to question many of the precepts of the Modern Movement. In particular, he questioned the ability of the International Style of Modernism to house the social spaces required by the latter half of the 20th century. In 1947, Kahn was appointed Professor at Yale University. He was to continue teaching throughout his architectural career, influencing a younger generation of architects along the way. His teaching enabled him to further develop his own concepts and to inform his ever-evolving definition of design. Kahn was drawn to investigate monumentality in architecture, creating buildings out of heavy, solid materials and forms and incorporating vivid plays of light, in complete contrast to the lightweight glass and steel structures being created elsewhere by his peers. This monumentality was also imbued with his concern for the ritual of human experience. His career, although extending to just over 20 years, was a rich and varied one, where he continually readdressed the issues of light, mass, structure and materials. Following a predominantly chronological order, this monograph identifies major themes and examines key works according to these themes. A comprehensive list of projects by Kahn spanning his lifetime and drawn from the Louis I. Kahn Collection at the University of Pennsylvania Archives is also included, listing over 231 projects, at least 30 of which were previously unattributed.