  What types of things counted as created substances for Descartes? Clearly, he takes an individual mind to be a created substance. If a mind did not have this status, then Descartes’s argument for its immortality, that it can be conceived apart from all else except God, and a fortiori from the body, would collapse. Beyond minds, however, an ambiguity appears. Although there are texts in which Descartes speaks of individual things like a piece of wax as substances, there are others—most famously, the Synopsis to the Meditations—that indicate that there is but a single extended substance, of which individual things are the modes. At a minimum, there is an asymmetry in his treatment of minds and material things, perhaps reflecting the tension between a hypokeimenon, accounting for difference, and the other sense of ousia, accounting for sameness. To say that Peter and Paul are substances is to say that their minds are numerically distinct; but to say that a piece of wax and a piece of wood are substances might be to say that they are both extended things.