 Spinoza's agreement with the Cartesian laws of nature and collision provides a telling set of further examples. Spinoza explicated and elaborated on these at length and in detail in the PCP. Interpreting this work as an expression of Spinoza's own thinking is a delicate matter, since its explicit aim is to present and explicate Descartes' views, not Spinoza's own. Despite this, the PCP provides a number of indications of where Spinoza diverges from Descartes on the metaphysical foundations of physics. In particular, the demonstrations Spinoza offers of most of the basic principles of Cartesian physics are often significantly different from or supplementary to Descartes' own, and seem to presage important elements of Spinoza's mature thought as expressed in the Ethics.