Abstract

The most common objection to the Fine-Tuning Argument for the Multiverse is that the argument commits the Inverse Gambler’s Fallacy. Simon Friederich has recently composed an interesting version of this fine-tuning argument that avoids this fallacy and better-matches important scientific instances of anthropic reasoning. My thesis in this paper is that this new argument, while it may avoid the fallacy, contains a disputable premise concerning the prior probabilities of the hypotheses at issue. I consider various ways to modify the argument to avoid this problem, but I argue that plausible replacements render other lines unjustified. I also briefly compare ‘indexical’ fine-tuning arguments such as Friederich’s, according to which our universe permits life, to ‘existential’ fine-tuning arguments, according to which some universe or other permits life. I conclude that while Friederich is correct that the new fine-tuning argument avoids the Inverse Gambler’s Fallacy, the argument nevertheless depends on an unjustified premise, and this is further reason for proponents of fine-tuning arguments for the multiverse to employ existential arguments rather than indexical arguments.