James Franklin (born 1953 in Sydney) is an Australian philosopher, mathematician and historian of ideas.
Franklin was educated at St. Joseph's College, Hunters Hill, New South Wales. His undergraduate work was at the University of Sydney (1971–74), where he attended St John's College and he was influenced by philosophers David Stove and David Armstrong. He completed his PhD in 1981 at the University of Warwick, on algebraic groups. Since 1981 he has taught in the School of Mathematics and Statistics at the University of New South Wales.
His research areas include the philosophy of mathematics and the 'formal sciences', the history of probability, Australian Catholic history, the parallel between ethics and mathematics (work for which he received the 2005 Eureka Prize for Research in Ethics), restraint, the quantification of rights in applied ethics, and the analysis of extreme risk. Franklin is the literary executor of David Stove.
His 2001 book, The Science of Conjecture: Evidence and Probability Before Pascal, covered the development of thinking about uncertain evidence over many centuries up to 1650. Its central theme was ancient and medieval work on the law of evidence, which developed concepts like half-proof, similar to modern proof beyond reasonable doubt, as well as analyses of aleatory contracts like insurance and gambling.