Ideas, Evidence, and Method: Hume’s Skepticism and Naturalism Concerning Knowledge and Causation by Graciela De Pierris (review)

De Pierris offers a reading that unites radical skepticism and normative naturalism as “two equally important and mutually complementary aspects of Hume’s philosophical position” (1–2). The “modern theory of ideas” shapes skepticism, and Newtonian methodology is the basis for naturalism.

The “modern theory of ideas” holds that evidence for optimal human cognition is grounded in the “immediate acquaintance with ostensive presentations that are or have been given to the mind” (2). This is the “presentational-phenomenological model of apprehension” (3). Descartes introduces to the model pure intellectual items, that is, clear and distinct ideas, which have “‘immutable and eternal’ essences or forms” as referents (6, 8). Locke’s “sensible model” (9) takes simple ideas of sensation to be clear and distinct and allows certain “knowledge of a relation of correspondence between simple ideas of sensation and external physical reality” (78). Hume is “neutral” on the “ontology or ultimate origin” of what is before the mind, and he focuses on the “immediate presentational features” as “independent of any possible external referent” (79). Hume’s “consistent” (4) commitment to the sensible model leads to a radical skepticism that exploits “the evidential gap when a putative cognition goes beyond what is or has been strictly perceived” (3).

Radical skepticism operates at a “meta-level” above normative naturalism (237). Hume’s “positive normativity” in common life and science is “a form of reflection which can be integrated with our basic natural beliefs” (16). This naturalism results from his “unwavering commitment” to a Newtonian scientific methodology applied to a science of the mind (viii). The “evidential standards” of Newton’s method inspire Hume’s positive theory of causation (15). Newton’s “Rules for the Study of Natural Philosophy” (Principia Mathematica III) inspire the causal rules in Hume’s Treatise of Human Nature 1.3.15. These rules are “normative standards of evidence based on observable phenomena” (15-16) and “prescribe how we reflectively engage in causal inductive inferences” (19).

Chapter 1 contextualizes the theory of ideas and knowledge by Descartes, Locke, and Leibniz. The second shows how Hume “radicalizes” the theory of ideas and transforms knowledge (199). How Hume appropriates Newton and departs from Locke on method and causality is the subject of the third. Chapter 4 defends a “skeptical inductivist” interpretation of the causal inference that emphasizes the dual role of the radical model and Newtonian method (200). The final chapter covers Hume’s naturalism and skepticism.

De Pierris’s main target is scholars who emphasize Hume’s naturalism and see radical skepticism as only a “vehicle” or clearing ground that prepares us for the embrace of mitigated skepticism and the positive science of human nature (1). Accordingly, the possibility of radical skepticism must remain open and must be “permanently available to us,” (305) or we “must have continual access to it” (302). Radical skepticism guards “against the continuing temptations of the supernatural,” as Hume provides “a non-theological foundation for morals and politics” (303).

I remain doubtful of the role of radical skepticism for at least three reasons. First, no reason is given why radical skepticism is confined to eliminating theological explanations. Hume’s use of radical skepticism is distinctively pervasive: he casts doubt on whether any of our beliefs are justified. Second, he does not make explicit connections between radical skepticism and the positive application of the science of the mind to passions, morals, and politics. Third, the adoption of moderate skepticism alone curbs religious dogma (e.g. Ryu Susato, Hume’s Sceptical Enlightenment, Edinburgh University Press, 2015, 14–15). De Pierris claims that radical skepticism limits “our inquiries to the realm of experience” to curb supernatural “flights of fancy,” but this is just the second species of mitigated skepticism distinguished by Hume (300–301).

Radical skepticism about any belief at any time may be possible. But Hume’s supposed “permanent disposition” to engage in radical skepticism has the...