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.