From Locke to Materialism: Empiricism, the Brain and the Stirrings of Ontology

Abstract

My topic is the materialist appropriation of empiricismas conveyed in the 'minimal credo' nihil est in intellectu quod non fuerit in sensu (which is not just a phrase repeated from Hobbes and Locke to Diderot, but significantly, is also a medical phrase used by Harvey, Mandeville and others). That is, canonical empiricists like Locke go out of their way to state that their project to investigate and articulate the 'logic of ideas' is not a scientific project: "I shall not at present meddle with the Physical consideration of the Mind" (Locke 1975, I.i.2), which Kant gets exactly wrong in his reading of Locke, in the Preface to the A edition of the first Critique. Indeed, I have suggested elsewhere, contrary to a prevalent reading of Locke, that the Essay is not the extension to the study of the mind of natural-philosophical methods; that he is actually not the "underlabourer" of Newton and Boyle he claims politely to be in the Epistle to the Reader (Wolfe and Salter 2009, Wolfe 2010). Rather, Locke says quite directly, "Our Business here is not to know all things, but those which concern our Conduct" (Locke 1975, I.i.6). There is more to say here about what this implies for our understanding of empiricism (see Norton 1981 and Gaukroger 2005), but instead I shall focus on a different aspect of this episode: how a non-naturalistic claim which belongs to what we now call epistemology (a claim about the senses as the source of knowledge) becomes an ontologymaterialism. That is, how an empiricist claim could shift from being about the sources of knowledge to being about the nature of reality (and/or the mind, in which case it needs, as Hartley saw and Diderot stated more overtly, an account of the relation between mental processes and the brain). (David Armstrong, for one, denied that there could be an identification between empiricism and materialism on this point [Armstrong 1968, 1978]: eighteenth-century history of science seems to prove him wrong.) Put differently, I want to examine the shift from Locke's logic of ideas to an eighteenth-century focus on what kind of 'world' the senses give us (Condillac), to an assertion that there is only one substance in the universe (Diderot, giving a materialist cast to Spinozism), and that we need an account of the material substrate of mental life. This is neither a 'scientific empiricism' nor a linear developmental process from philosophical empiricism to natural science, but something else again: the unpredictable emergence of an ontology on empiricist grounds. 42 Willis 1683 = Two Discourses, ch. X, 5. Mandeville also approvingly discusses the nihil est principlehere, that our knowledge of natural things comes from the sensesand credits Sylvius as the source (Mandeville 1730/1976, vi), but the idea is clearly being put to more philosophical use.