Naturalized epistemology
Authors: Brown Curtis , Luper Steven 
Published: September 2018

Epistemology, the theory of knowledge, is one of the central areas of philosophy. The questions addressed by epistemology have historically included what knowledge is, how we can or should achieve it, and how much, if anything, we can know. Naturalism is the view that the world contains only natural phenomena, and that the appropriate methods for acquiring knowledge of the world are those of the sciences. The term ‘naturalized epistemology’ was introduced by W. V. Quine in his 1969 essay ‘Epistemology Naturalized’, in which he argues that epistemology should be regarded as continuous with, or even part of, natural science.
Epistemological naturalists often contrast their approach with that taken by René Descartes. Descartes held that knowledge has a foundational structure. At the foundation are beliefs which we ‘clearly and distinctly perceive’, and about which we are therefore completely certain. For Descartes, these include beliefs about the contents and operations of our own minds. Other beliefs must be inferred from these foundational beliefs in order for us to be justified in holding them. Until we can show, on the basis of foundational beliefs, that there is a world outside our own minds, and that proper scientific methods will reliably give us information about it, we can have no confidence in the results of the sciences.
Advocates of a naturalized epistemology see the role of epistemology very differently. For them, philosophy does not come prior to science. The starting point of epistemology should not be our introspective awareness of our own conscious experience, but rather the conception of the larger world that we get from common sense and science. Most naturalists would also reject many other features of Descartes’ epistemology, including the view that knowledge requires certainty, the view that all our knowledge must be inferred from foundational beliefs, and the view that it is possible to know substantive facts about the world a priori, that is, without needing experience to provide evidence of their truth.
Of the three main epistemological issues, i.e. the nature of knowledge, the means of acquiring it, and its extent, Quine’s naturalized epistemology focuses on the second, the issue of how knowledge is acquired. In a famous passage, Quine describes what he sees as the proper subject of naturalized epistemology:
It studies a natural phenomenon, viz., a physical human subject. This human subject is accorded a certain experimentally controlled input – certain patterns of irradiation in assorted frequencies, for instance – and in the fullness of time the subject delivers as output a description of the three-dimensional external world and its history. The relation between the meagre input and the torrential output is a relation that we are prompted to study for somewhat the same reasons that always prompted epistemology; namely, in order to see how evidence relates to theory, and in what ways one’s theory of nature transcends any available evidence.
(Quine 1969: 82–3)
For Quine, then, naturalized epistemology is the empirical study of how human beings develop a theory of the natural world on the basis of their sensory inputs. Given this understanding of epistemology, it is clear why Quine thinks that ‘epistemology, or something like it, simply falls into place as a chapter of psychology’.
However, much of epistemology as traditionally conceived seems to be left out of Quine’s picture, and contemporary epistemological naturalists differ in how they think these topics should be addressed. First, one of the main concerns of epistemology has been to understand what knowledge is, in the sense of identifying necessary and sufficient conditions for knowing something. This seems to require an analysis of the concept of knowledge rather than an empirical investigation of the natural world. Some naturalists believe that epistemology should simply abandon conceptual analysis; some accept that conceptual analysis is a necessary and nonscientific part of epistemology, and conclude that only parts of epistemology can be naturalized; and some hold that conceptual analysis itself should become an experimental discipline.
A second aspect of traditional epistemology that Quine seems to neglect concerns the second epistemological question, that of how we do or should acquire knowledge. Many critics of Quine have noted that by focusing exclusively on the descriptive issue of how we in fact base a rich theory of the world on limited evidence, Quine appears to neglect normative issues about how we ought to modify our beliefs in light of new evidence. Some moderate epistemological naturalists concede that such issues cannot be regarded as part of science, while others have suggested that even normative issues can be naturalized.
A final issue that Quine pays little attention to relates to the third epistemological issue, that of how much knowledge, if any, we can have. Quine recommends treating the issue of the extent of our knowledge as internal to science. However, a main focus of traditional epistemology has been to address whether it is possible to convincingly refute radical scepticism, the idea that all or most of our beliefs could be seriously mistaken. To address this question by appealing to the results of science seems to beg the question. Can there be a naturalistic response to radical scepticism? Most contemporary naturalists would concede that they cannot refute scepticism, but would also hold that the only sceptical doubts worth taking seriously are those that arise from within science itself.