[5] Although his subjects were wide-ranging, he was particularly interested in the philosophy and practices of the English Arts and Crafts movement, whose emphasis on function, modesty, understatement, individuality and honesty to materials he saw as alternatives to the ostentatious historicism and obsession with ornament in German nineteenth century architecture, and whose efforts to bring a sense of craftsmanship to industrial design he saw as a significant national economic benefit.

As well as his official reports, Muthesius also developed a career as an author, communicating his ideas and observations in an influential series of books and articles that saw him become a significant cultural figure in Germany, culminating in Das englische Haus.

"[7] Muthesius returned to Germany in 1904 and established himself as an architect in private practice, while retaining a role as an official advisor to the Government of Prussia focusing his time on reforming art and design education in order that more emphasis be put on workshop training.

In 1907 he was accused by the Fachverband für die wirtschaftlichen Interessen des Kunstgewerbes ("Trade Association for the Economic Interests of the Arts and Crafts") of criticising the quality of German industrial products in a lecture in Berlin.

The Deutscher Werkbund was a major influence on the early careers of Le Corbusier, Walter Gropius and Mies van der Rohe, but although Muthesius was in many ways its spiritual father and served as its chairman from 1910 until 1916, he had little sympathy with the emerging early-modernism, considering both Art Nouveau and the later designs of the Bauhaus to be just as much superficial styles as those of the nineteenth century.