Fine-Tuning and the Scope of Physical Laws

Fine-tuning arguments claim that the precise parameter values and initial conditions required for complexity and life are extraordinarily improbable and demand explanation. This article examines whether such probability claims can be grounded in physics. A brief study of a historical case, Isaac Newton’s design argument regarding the solar system, illustrates that assessments of “improbable coincidences” can result from overly narrow theoretical perspectives. The article then distinguishes between probabilities legitimately employed within physical theories and those invoked in fine-tuning arguments. While physics provides mathematical structures and dynamical justifications for probability assignments, fine-tuning arguments typically rely on unjustified applications of the principle of indifference over possibility spaces lacking unique measures. An appealing reformulation of the fine-tuning argument, due to John Roberts, avoids this and other challenges, but the argument clearly depends on what the Designer regards as aim worthy rather than physics. Closer examination of the aspects of physics routinely used in fine-tuning arguments exposes problems. “Naturalness” in particle physics conflates distinct concepts—autonomy of scales versus statistical typicality within theory space—where only the former is well motivated. Cosmological measures lack the dynamical grounding that justifies using them to make probabilistic claims similar to equilibrium statistical mechanics. The article concludes that fine-tuning arguments fail to establish their probabilistic claims, and as a result, fail to provide a version of the argument from design that should compel those not already committed to rationalist explanatory demands.