b. 1940
John Leslie (born 1940) is a Canadian philosopher and emeritus professor at the University of Guelph, best known for his work on cosmological fine-tuning, the anthropic principle, and axiarchism. He has written extensively on why the universe exists and why its constants appear life-permitting, arguing that ethical requirements—not mere chance—may explain cosmic structure. His probabilistic approach to teleological reasoning has made him a central figure in philosophy of cosmology.
Developed influential formulations of the fine-tuning argument using probabilistic and anthropic reasoning
Defended axiarchism: the view that ethical necessity explains why something exists rather than nothing
Authored Universes (1989), a landmark treatment of fine-tuning and the many-worlds hypothesis
Contributed to the Doomsday Argument literature, examining observer-selection effects and human extinction risk
Authored Infinite Minds (2001), exploring panpsychist and Neoplatonist metaphysics