Naturalness, Extra-Empirical Theory Assessments, and the Implications of Skepticism
James D. Wells
Abstract: Naturalness is an extra-empirical quality that aims to assess plausibility of a theory. Finetuning measures are one way to quantify the task. However, knowing statistical distributions on parameters appears necessary for rigor. Such meta-theories are not known yet. A critical discussion of these issues is presented, including their possible resolutions in fixed points. Skepticism of naturalness’s utility remains credible, as is skepticism to any extra-empirical theory assessment (SEETA) that claims to identify “more correct” theories that are equally empirically adequate. Specifically to naturalness, SEETA implies that one must accept all concordant theory points as a priori equally plausible, with the practical implication that a theory can never have its plausibility status diminished by even a “massive reduction” of its viable parameter space as long as a single theory point still survives. A second implication of SEETA suggests that only falsifiable theories allow their plausibility status to change, but only after discovery or after null experiments with total theory coverage. And a third implication of SEETA is that theory preference then becomes not about what theory is more correct but what theory is practically more advantageous, such as fewer parameters, easier to calculate, or has new experimental signatures to pursue.