 But is it obvious that powers or forces are not relations of distance? This question along with the questions about how powers or forces relate to the more obvious properties of extension—for instance, size and shape—raise interesting and important questions that go to the heart of the PN argument. The main intuitive thrust behind Malebranche’s PN argument is to convince the reader that, if we understand the Cartesian conception of matter or extension properly, we can see that motive force or power is neither necessary nor sufficient for being an extended  substance.[16]  This view seem rather close to Descartes’ original insight that having specific spatial features and standing in particular spatial relations to other bodies are both necessary and sufficient conditions to be a bodily  substance,[17]  and Malebranche takes this to imply that whether these bodies further possess a motive force is an issue peripheral to the basic nature of bodies. Such a view seems to be expressed in his discussion of motion and rest in the Search: