In a series of books from 1983 to 1996, I have examined various themes in seventeenth- and eighteenth-century philosophical writings. In Perceptual Acquaintance from Descartes to Reid (University of Minnesota Press and Blackwell, 1984), the themes primarily related to perception and our knowledge of external objects. The pervasive notion of “presence to the mind, ” with its accompanying principle of “no thing can be or act where it is not, ” raised puzzles about how the mental can relate to the physical. The implication often was that there can be no cognition at a distance. The consequences of these notions and principles seemed to be that we cannot know objects directly or in themselves. Those who grappled with these consequences, both well-known and lesser-known writers, struggled to find a way of breaking out of what some later commentators described as the “veil of ideas. ” Perceptual Acquaintance explored various interpretations of the nature of ideas and of the relation, causal or epistemic, between the perceiver and the world.
Thinking Matter: Materialism in Eighteenth-Century Britain (University of Minnesota Press and Blackwell, 1983) examined Locke's fascinating suggestion that God could have made thought a property of organized matter, presumably the brain, instead of making it a property of immaterial substance. The possibility that matter could be active, that it could be the substance or subject of both extension and thought, threatened many accepted views about the immateriality of the soul, to say nothing of traditional morality. That possibility also reinforced the newly emerging concept of matter, matter as active force and power instead of the older passive corpuscular structure waiting to be activated by God or other spirits. This newer concept had implications for perception theory, the nature of the objects we know, and the relation between ideas and objects.
There were three theories about this relation: occasionalism, preestablished harmony and physical influence. I gave a detailed account of