Aristotle and Descartes in Spinoza’s Approach to Matter and Body

Considered in its seventeenth-century context, Spinoza’s way of thinking about substance and nature is striking for its simultaneous refusal of Cartesian dualism and Hobbesian materialism. Spinoza knew both thinkers’ work well, yet sided with neither. Where Descartes divides substance into thinking and extended substance, and where Hobbes reduces all things to body, Spinoza espouses what is best called a double-aspect or non-reductive monism. The single substance of the Ethics is expressed as an infinity of modes in an infinity of attributes, each infinite in kind. Thought and extension are two of the infinite attributes of substance, and the simultaneous sameness and difference of thought and extension constitutes a major theme of the Ethics. Using exactly parallel demonstrations, Spinoza argues in the second part of the Ethics that substance, or God, or nature is equally a thinking thing and an extended thing. Descartes’ account of matter and extension, in which passive matter is set in motion by God, inspires harsh criticism from Spinoza