How does Locke contribute to the development of projects for a science of the mind, even though he seems to reject or at least bracket off such projects himself? A canonical empiricist, Locke nevertheless goes out of his way to state that his 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” (Essay, I.i.2). Locke further specifies that his analysis of mental processes will not engage with knowledge of the brain (even though he had been the student of Thomas Willis). Now, Kant seemed to make an elementary mistake, given Locke’s clear statement, when he claimed that Locke’s project was a “physiology of the understanding” (KRV, Preface to A edition). If Locke’s project was not a physiology of the understanding, what might this have been? Thus I examine, not the well-studied fortunes of Lockean thinking matter, but Locke’s impact on scientific treatments of the mind, including in the sense of a ‘naturalization’ of the mind. Because if Kant made this charge, many 18th-century thinkers in fact positively treated Locke as their great forerunner in psychological fields, Charles Bonnet and Joseph Priestley among them, just as some prominent physicians such as Cabanis claimed to be ‘finishing the job’ that Locke had started in, e.g. their materialist theories of the passions. The ‘Locke Problem’ here is: how can one reconcile empiricism and claims about cerebral processes, while seeking to remain a Lockean?

Allen’s book entitled David Hartley on Human Nature (1999) gives a careful review of the works and life of the physician and philosopher David Hartley (1705-1757). However, there has been no thorough study of the role of nerves in the naturalisation of the mind in Hartley’s work. This latter, in his Observations on Man, his Frame, his Duty, and his Expectations first published in 1749, discusses the nature of sensations and ideas. Thereby, he takes position on famous notions of physics, physiology, and psychology of his time. In following the account of association in John Gay’s Dissertation on the Fundamental Principles of Virtue, which states the possibility to explain mental pleasures and plains on the basis of association, Hartley wants to show the physical cause of this latter, as well as its moral consequences. He is very inspired by Newton, both for the theory of vibrations, and the conception of nerves as capillary. Rejecting Boerhaave’s idea of tubular nerves in which the animal spirits flow, he sketches nerves as constituted by infinitesimal particles vibrating in aether. Although his explanation of sensations, ideas, and motions, is strictly materialist, Hartley insists on their mental status. By accounting for mental facts with considerations about infinitesimal material processes, the philosopher is able to show that associations of ideas actually have the power to modify the vibrating structure of our brain. It is interesting to see, from a historical point of view, how far Hartley takes the Lockean project of naturalisation of the mind.

Anatomy is a widespread metaphor among eighteenth-century British authors. Besides its proper meaning in medical contexts, ‘anatomy’ is frequently put into phrases such as ‘anatomy of nature’, ‘of the mind’, ‘of human nature’, or ‘of the light’. The common core of these different uses refers to some methodized study of the realm or phenomenon to which it is attached. In the present paper I try to reconstruct the meanings attached to ‘anatomy’ in moral contexts, i.e. in the context of the study of the mind and human nature. As this anatomical enterprise meant different things to various key actors from Locke to Reid, I will try to offer a typology by showing that various projects can be characterized as predominantly descriptive anatomies aiming at the delineation of the mind’s part (as in e.g. Locke’s case), and as predominantly functional anatomies aiming at the excavation of explanatory principles of the mind’s functioning (as e.g. in Hume’s case). I will explore the features of various attempts, thereby 1) locating them on the methodological map of eighteenth-century natural and moral inquiry with a sensitivity to how they are related to dominant methodological influences springing from Baconian and Newtonian legacies; 2) reconstructing how conceptual connections, or the lack thereof, between anatomies of the mind and anatomy proper is reflected in various stances taken on the mind-body problem in this context; 3) and exploring how anatomies of mind reflect attitudes towards religious values ranging form providential naturalism to methodological atheism.

In his Essay Concerning Human Understanding John Locke gives two explanations of intellectual habits and the association of ideas, one a psychophysiological account that has its origins in the Cartesian science of the brain, and the other a purely psychological account that seems to be original with Locke himself. After laying out Locke’s two positions and showing how each fits into the larger project of the Essay, we trace them the first to Locke’s reading of Nicholas Malebranche’s Recherche de la Vérité and ultimately to Descartes’ Traité de l’homme. These models explain habit and association in terms of the flow of nervous fluids creating traces in the brain. The second explanation is based on the speed with which ideas pass through the mind after frequent repetition. Locke uses it to explain why we falsely believe that we “see” three dimensionality. This psychological explanation was taken up by George Berkeley in his New Theory of Vision, and by other 18th-century writers. However, the psychophysiological explanation also persisted throughout this period among both philosophers and medical writers including Hermann Boerhaave and Albrecht Haller. An alternate psychophysiological explanation briefly flourished based on the Queries at the end of Newton’s Optics, and adopted by David Hartley in his Observations on Man. Nevertheless, it was the Cartesian brain-trace explanation which predominated throughout this period, and is even to be found at the end of the nineteenth-century in William James’ discussion of habit and association in his Principles of Psychology.