  Leibniz thus grants that while physical extension is to be ascribed  to the bodies of physics, it is not to be treated as a basic or  fundamental property of matter. Rather, physical extension itself is  to be understood as a repetition, or distribution, of more basic  forces. Leibniz’s radical suggestion would, in effect, turn the  Cartesian understanding of matter on its head: whereas, for example,  Descartes attempted to explain solidity in terms of physical   extension,[14]  Leibniz proposes to explain physical extension in terms of solidity  – a body isn’t solid because it is extended, it is  extended because it has the ability to exclude other bodies! 