Likelihoods, Multiple Universes, and Epistemic Context

puzzle physicists and philosophers alike and provide the lynchpin for the fine-tuning argument for design. But both advocates and opponents of the fine-tuning argument treat multiple universes with a selection effect as an entirely respectable hypothesis to account for the constant values. I will argue that, except where there is relevant prior information, the existence of multiple instances of a low-likelihood causal process cannot legitimately be used as an alternative to a different, higher-likelihood causal process. This conclusion is relevant to the fine-tuning debate but also has interest for those who hold, as I do, that the fine-tuning argument is flawed in any event. I have argued elsewhere that the fine-tuning argument for a designed universe does not work because there is no well-defined probability for the values of the constants on the hypothesis of no design or “chance.” This view renders the postulation of multiple undesigned universes moot, as multiplying an undefined probability many times yields an undefined probability. Furthermore, I have argued elsewhere that the action of an agent should not automatically be treated as ranging over the entirety of a group of trials, even when those trials are independently known to exist, and that a larger group of trials is only relevant to a comparative inference when both hypotheses are equally relevant to the entire group of trials. This consideration casts doubt on the relevance of multiple universes in the fine-tuning argument, since design by an agent is one of the alternatives.