Christopher Alexander (born October 4, 1936 in Vienna, Austria) is an architect noted for his theories about design, and for more than 200 building projects in California, Japan, Mexico and around the world. Reasoning that users know more about the buildings they need than any architect could, he produced and validated (in collaboration with Sarah Ishikawa and Murray Silverstein) a "pattern language" designed to empower any human being to design and build at any scale. Alexander was a licensed contractor and architect in England. In 1958 he moved to the United States, and has lived in Berkeley, California from 1963 until the present. He is professor emeritus at the University of California, Berkeley.