Observer-Relative Chances in Anthropic Reasoning? 1

Here we examine an argument by John Leslie (Leslie 1997) purporting to show that anthropic reasoning gives rise to paradoxical “observer-relative chances”. ² We show that the argument trades on the sense/reference ambiguity and is fallacious. We then describe a different case where chances are observer-relative in an interesting, but not paradoxical way. The result can be generalized: at least for a very wide range of cases, SSA does not engender paradoxical observer-relative chances.