Seventeenth-century atomist David Gorlaeus rejects Aristotelian forms and real universals in things while accepting components of Aristotelian accounts of knowledge including sensible species, the immateriality of the intellect and key features of realist theories of universals. To resolve two puzzles raised by his theory of knowledge I interpret Gorlaeus’ claims about universals in light of a contemporaneous Aristotelian view. Whether the puzzles are adequately resolved or not, they create a problem space within which figures like Descartes and Locke developed their views on the role of universals in scientific knowledge.

In this paper I address the vexed question of secondary causation in Rene Descartes' physics, and examine several influential interpretations, especially the one recently rpoposed by Dennis Des Chene. Iargue that interpreters who regard Cartesian bodies as real socondary causes, on the grounds that the modes of body include real forces, contradict Descartes' account of modes. On the other hand, those who deny that Descartes affirms secondary causation, on the grounds that forces cannot be modes of extension, commit Descartes to the problematic view that the undetermined and immutable will of God is the sole cause of determinate and variable motions. Des Chene's contextualist aproach to Descartes' texts leads him to an intermediate position that combines elements of both interpretations. However, in my view, Des Chene's interpretation likewise fails to resolve aparent tensions in Descartes' claims. i thus propose to separate the issue of force'. On the basis of this approach, and a study of Jesuit commentaries familiar to Descartes, I develop a new interpretation which takes seriously Descartes' claim that the laws of nature are the secondary and particular causes of particular motions and changes in motion.