Prof. Keith Critchlow (1933–2020) was a well-known lecturer and author and a founding member of Research Into Lost Knowledge Organization (RILKO), a founding member and Director of Studies of Kairos, and a founding member and President of the Temenos Academy. He was Professor Emeritus and founder of the Visual Islamic and Traditional Arts Programme at the Royal College of Art, now the Prince’s School of Traditional Arts. Trained as a painter, Critchlow discovered geometry intuitively. A period of intensive geometric practice (and work with Buckminster Fuller) led him to the recognition that the universal principles of geometry are revealed and confirmed both by the area of design where art and mathematics meet and in the study of nature and ancient and medieval sacred cosmological stone, temple, cathedral, and mosque architectures. Keith Critchlow had been a senior lecturer at the Architectural Association in London, and taught Islamic Art at the Royal College of Art. He also participated as geometer in various sacred architectural projects. His books include Islamic Patterns: An Analytical and Cosmological Approach (1999); Time Stands Still: New Light on Megalithic Science (2007); and The Hidden Geometry of Flowers: Living Rhythms, Form, and Number (2011).