Expounds and defends the thesis that Descartes, most of the time, accepted a subjectivist theory of modality according to which a proposition's being necessary is its relating in a certain way to our thought. Several difficult and long-standing problems, and some others that have been neglected, are solved or lessened by this thesis. One is voluntarism—the thesis that God voluntarily gives modal truths their truth-value. It is shown that Descartes is nearly always careful to say not that God cannot lie but that he does not lie.
Keywords: Descartes, God, modality, subjectivism, voluntarism