Christopher Isham is a Senior Research Investigator and Emeritus Professor of Theoretical Physics at Imperial College London. He is a former Senior Dean of the College. Dr Isham has made many important contributions in the fields of quantum gravity and the foundations of quantum mechanics. Motivated by the "problem of time" in quantum gravity, he developed a new approach to quantum theory known as the "HPO formalism" that enables the theory to be extended to situations where there is no normal notion of time (such as in Einstein's theory of general relativity). Since the late 1990s, Dr. Isham has been developing a completely new approach to formulating theories of physics based on the mathematical concept of a "topos". This gives us a radically new way of understanding the traditional problems of quantum theory as well as providing a framework in which to develop new theories that would not have been conceived using standard mathematics. From 2001 to 2005, Dr. Isham was a member of Perimeter Institute’s Scientific Advisory Committee; during the last year he was the Chair of the Committee.