Lyon, AidanAlastair Wilson2015-12-089780199673421http://hdl.handle.net/1885/36773Humphreys� Paradox (Humphreys 1985) can be solved if propensity theorists (i) adopt R�nyi�s 1955 probability axiom system as the correct axiom system for propensities and (ii) maintain that there are no backwards propensities in the world. A similar move can be used to solve Milne�s Problem (Milne 1985)�another common objection to the propensity interpretation. That�s the good news. However, Humphreys� Paradox and Milne�s Problem are just two special cases of a much more general problem, and this problem causes trouble even for propensity theorists who accept (i) and (ii). That�s the bad news.201410.1093/acprof:oso/9780199673421.003.00062020-12-27