Leslie, M.Litt. (Oxford), F.R.S.C. taught philosophy at the
University of Guelph; retired, he is
now an Adjunct Professor at the
University of Victoria. A Fellow of the
Royal Society of Canada, he was the British Academy Royal
Canada Exchange Lecturer for 1998. He has held visiting professorships in
the Research School of Philosophy at
Australian National University, in
the Department of Religious Studies at the
University of Calgary, and at
the Institute of Astrophysics at the
His Value and Existence (1979) defended the Platonic theory that the cosmos might exist because of an ethical requirement. Work on this and other themes in philosophy of religion made him interested in the fine-tuning of cosmic parameters in ways that made it possible for intelligent life to evolve. He became known in philosophy of cosmology for numerous articles, for his book Universes (1989) and for the edited volume Physical Cosmology and Philosophy (1990; later expanded as Modern Philosophy and Cosmology).
Any cosmic fine-tuning might be explained either through divine action or through “anthropic” observational selection for there might exist many universes, very varied in their characteristics, observers being able to find themselves only in universes whose characteristics were not utterly hostile to them. Such observational selection would also make observers more likely to find themselves at times and places where observers were common, not rare. If the human race had been destined to colonize its entire galaxy, wouldn’t any human expect to find himself or herself at a time when it had indeed done so, instead of at one when the vast majority of all humans were in the future? This is the basis of a “doomsday argument” which warns us not to be confident in a long future for humankind. John wrote many articles defending the argument. It is central to his The End of the World: The Science and Ethics of Human Extinction (1996), a book which also contains a detailed survey of current threats to the human race, plus discussion of why its extinction would be tragic. This book is also available as an online eBook.
John’s latest book is Infinite Minds: A Philosophical Cosmology, also available as an online eBook. He is the inventor of “chess variant of the decade” Hostage Chess.