  (4) A final passive property of bodies might go without mention if  not for the special twist that Leibniz puts on it. Even while arguing against the Cartesian thesis that the whole essence of matter is  extension, Leibniz could hardly deny that bodies as they are studied  by physicists are extended, or if one prefers, that they have the  property of physical extension. Nonetheless, Leibniz intriguingly  suggests that physical extension – far from constituting the  whole essence of matter – is not even a basic property of  bodies. In an informative piece dated to 1702, Leibniz writes: