The Argument from Reason

This monograph presents a comprehensive defense and elaboration of C.S. Lewis's argument from reason against metaphysical naturalism. Reppert contends that naturalism, the view that reality consists solely of physical entities governed by natural laws, cannot adequately account for the rationality of human reasoning. The work systematically develops the claim that if naturalism were true, our cognitive faculties would be products of non-rational physical processes, thereby undermining any confidence in their reliability, including confidence in naturalism itself.

The author reconstructs Lewis's original argument while addressing decades of philosophical criticisms and refinements. Central to Reppert's analysis is the distinction between reasons and causes. He argues that naturalism reduces all mental events to physical causes, leaving no room for genuine rational inference where beliefs are held because of logical grounds rather than mere causal determination. The work examines how naturalistic explanations of mind, whether through evolutionary theory, neuroscience, or computational models, fail to bridge the explanatory gap between physical processes and rational thought.

Reppert engages extensively with prominent naturalist philosophers including Daniel Dennett, Paul Churchland, and Patricia Churchland, demonstrating how their eliminative and reductive approaches to consciousness cannot preserve the normative dimension of reasoning. He argues that attempts to naturalize intentionality and mental causation either eliminate the phenomena they purport to explain or smuggle in non-naturalistic assumptions. The monograph also addresses evolutionary arguments, contending that natural selection might produce reliable belief-forming mechanisms for survival but cannot guarantee mechanisms that track truth, especially in abstract domains like mathematics, logic, and philosophy.

The work's significance lies in its rigorous philosophical defense of a theistic argument often dismissed in academic circles. Reppert shows how the argument from reason remains resilient against naturalistic critiques and provides grounds for considering alternatives to naturalism. While not explicitly developing a positive theistic metaphysics, the monograph argues that accounting for reason requires resources beyond those available to naturalism, pointing toward worldviews that ground rationality in a transcendent source. The argument thus contributes to contemporary debates about consciousness, intentionality, and the limits of scientific materialism, demonstrating that questions about human reason bear directly on fundamental metaphysical choices between naturalistic and theistic worldviews.