In 1926 philosopher Ludwig Wittgenstein designed and built a house in Vienna for his sister. The only building designed by Wittgenstein, it crystallized his philosophy of architecture - notable for its clarity, precision, and austerity - and served as a foil for his written work. This book presents a detailed investigation of the house, based on 30 years of extensive research. It examines the formal properties of the structure, including Wittgenstein's attention to proportion, detail, and colour. It is also the story of one man's relationship to the building: in 1971, author Bernhard Leitner was instrumental in saving the wittgenstein house from destruction and having it declared as a national landmark. In the years since, he has continuously refined his ideas about the house and its architect. The photographs are accompanied by archival images showing the house as it was originally built, before numerous alterations.