(RNS) Fifty years after his death, not many people can claim to have known C.S. Lewis personally. But one of them is James Houston, one of the founders of the respected Christian institution Regent College in Vancouver, who ran in the same circles as Lewis while they were both at Oxford. Houston, who turned 91 on Thursday (Nov. 21), a day before the 50th anniversary of Lewis’ death, still teaches theology at Regent and co-founded the C.S. Lewis Institute in Washington, D.C. He spoke with RNS about Lewis’ strengths and weaknesses, his triumphs and shortcomings. This interview has been edited for length and clarity.