This is a scholarly examination of the theoretical work of one of the most important architects of early modern Europe. Trained as a scientist, Wren applied the seventeenth-century scientific methods to his study of ancient, medieval, Renaissance and contemporary architecture. From his study of ancient buildings, he posited a new version of the origins and development of the Classical style, thereby becoming one of the first to challenge theoretical principles of architecture that had been upheld since the Renaissance. Rejecting the idea of beauty as absolute and innate, Wren formulated an empirical definition, based on visual perception and custom. His acceptance of the relativity of beauty also led him to recognize the Gothic style, then disparaged by himself and his contemporaries throughout Europe, as a legitimate one that evolved within particular cultural circumstances. This edition of Wren's writings includes accurate, annotated transcriptions of the texts.