A lecture on the “Monty Hall Problem”, one of the most striking puzzles for probability. Professor Stewart here gives the problem as something like the following:
You have a choice of three doors: Behind one of them is Andromeda, but behind the other two is a Gorgon. Perseus suggests the tactic of choosing the one door and then sticking with it, even after another door is opened and he is given the chance to swap. In contrast, Pigasus suggests the tactic of always switching the chosen door once one of the two alternative doors are opened. Who has the better option?

Ian Stewart read Mathematics at Churchill College, Cambridge before completing his doctorate at the University of Warwick where he is now a Professor of Maths. He was the first recipient of the Christopher Zeeman medal and has held visiting professorships in the United States, Germany and New Zealand. He has given the Royal Institution Christmas lectures and is a fellow of the Royal Society. He was the Gresham Professor of Geometry between 1994 and 1998.