 One way of accounting for divergent claims in different texts is to say that Leibniz had different views on the issue over time. There is no question that Leibniz’s views on substance changed to some degree over the course of his career (exactly how much they changed is one of the most contentious issues in Leibniz scholarship). However, the developmental strategy is more difficult (though not impossible) to deploy in the present case because both texts were written around the same time in 1714. Another possibility (suggested in the secondary literature) is that Leibniz is exploring different theories of substance at this point in his career. Though he is tempted by a strictly monadological metaphysics (as presented in the Monadologie), he is also considering an ontology that countenances the existence of simple substances and corporeal substances (where corporeal substances are “animals” as described in the previous paragraph). Leibniz is laying out this latter theory in The Principes de la Nature et de la Grace (see Hartz 2007). There are some prima facie reasons for resisting an interpretation along these lines (though it cannot be conclusively ruled out). First, Leibniz does not describe himself as a “theory pluralist” with respect to substance. As we have seen, Leibniz consistently refers to his philosophy as a (single) system. This is one of the things that make it amenable to the geometric model of demonstration.  When Leibniz addresses the fact that he has not unfolded his entire system in a single work, he emphasizes that this is not because he has not thought the system all the way through. In one of his less modest moments he writes to Burnett, for example: