Naturalized Epistemology

Core Idea

Naturalized epistemology, proposed by Quine in his 1969 essay 'Epistemology Naturalized,' argues that traditional epistemology's project of grounding all knowledge in a foundation of certainty has failed and should be replaced by (or at least supplemented with) empirical investigation of how humans actually form beliefs. On Quine's radical replacement thesis, epistemology becomes a chapter of psychology: we study the causal relationship between sensory input and theoretical output without worrying about normative questions of justification. More moderate naturalizers (Goldman, Kornblith) retain the normative dimension but insist that epistemology must be informed by cognitive science, evolutionary psychology, and the empirical study of reasoning biases. The central tension is between normativity and description: can an empirical study of how we do reason tell us how we ought to reason, or does collapsing that distinction eliminate what makes epistemology philosophical?

How It's Best Learned

Start with Quine's diagnosis: Carnap's attempt to rationally reconstruct all knowledge from sense experience failed, and no successor program has done better. If the a priori foundation cannot be secured, perhaps we should abandon the quest and instead study knowledge formation as a natural phenomenon. Then ask: does this move preserve or destroy what epistemology is supposed to do?

Common Misconceptions

• Naturalized epistemology does not necessarily deny that there are norms of reasoning; moderate versions hold that empirical findings (e.g., about cognitive biases) can inform normative epistemology without replacing it.
• Quine's proposal is not simply the claim that science is relevant to philosophy; it is the more radical claim that the traditional project of providing a non-circular justification for empirical knowledge is unachievable and should be abandoned.

Explainer

Your prerequisites in "what is knowledge" and the rationalism-vs-empiricism debate introduced you to the traditional epistemological project: provide a foundation for knowledge that does not assume what it is trying to justify. Descartes sought certainty in the cogito; Locke and Hume grounded knowledge in sense impressions; Kant tried to identify the a priori categories that structure experience. Naturalized epistemology begins with Quine's diagnosis that every version of this project has failed — and draws a radical conclusion about what to do next.

Quine's target in "Epistemology Naturalized" (1969) was Rudolf Carnap's logical empiricist program, which attempted to translate all empirical statements into a formal language built from sense-data reports. If this had succeeded, we would have a chain running from raw sensory inputs up to the theoretical claims of science, with each step logically certified. Quine argued it cannot work, for two reasons. First, Hume's problem of induction cannot be solved: no amount of past observations logically guarantees any future observation. Second, Duhem's holism means that individual scientific statements cannot be separately confirmed or disconfirmed by experience — they face experience as a corporate body, and any statement can be retained in the face of contrary evidence by adjusting other statements. There is no way to anchor the system to experience one statement at a time.

If the traditional project is hopeless, what should epistemology become? Quine's answer is the replacement thesis: abandon the normative project of justifying knowledge and replace it with the empirical project of describing how humans actually form beliefs. Epistemology becomes a chapter of psychology — specifically, the study of how sensory inputs (physical stimulations of sensory receptors) produce the theoretical outputs we call scientific beliefs. This is naturalism: treat human knowing as a natural phenomenon, subject to ordinary scientific investigation, without the privileged standpoint of a priori philosophical reflection.

The most serious objection to Quine's radical version is the normativity problem. Epistemology is supposed to tell us not just how we reason but how we *should* reason. An empirical description of human belief formation — including all our documented cognitive biases, motivated reasoning, and statistical errors — describes epistemic failure as much as epistemic success. How can studying how we actually reason tell us which reasoning is good? Quine's response (contested) is that science itself embeds norms of evidence and rational revision; by doing science about science, we inherit those norms without needing an external philosophical foundation for them. This answer satisfies some philosophers and strikes others as simply relocating the problem.

Moderate naturalizers like Alvin Goldman and Hilary Kornblith keep the normative dimension but insist that epistemology cannot ignore empirical findings. On this view, traditional epistemology went wrong not by being normative but by reasoning in an armchair about knowledge when cognitive science, evolutionary psychology, and the study of reasoning biases can directly inform those questions. What counts as a reliable belief-forming process? What cognitive mechanisms actually track truth? These are empirical questions, and a normative epistemology that ignores the answers is building in a vacuum. Naturalized epistemology in this moderate form is now mainstream: few epistemologists think they can simply ignore what psychology tells us about how humans reason.