 Leibniz’s side of the correspondence with Clarke is methodologically characteristic: he leaves much of his own systematic and complex metaphysical theorizing—including the monadology—in the background, bringing to the fore only those elements that are both necessary for his criticisms of the Newtonians and also likely to garner support from Clarke. Thus the key to many of Leibniz’s criticisms is the principle of sufficient reason (PSR), which he knows Clarke will endorse (although with a distinct conception of its scope: Leibniz asserts, while Clarke denies, that the principle demands that each act of divine willing requires a reason; for Clarke, divine willing itself is reason enough for some physical state of affairs to obtain, or event to occur). Leibniz argues in particular that several key aspects of the Newtonian worldview are simply incompatible with the PSR, including the idea of absolute space. If space were in fact completely independent of all physical objects and all relations among them, as the Newtonians seem to assert, then a problem arises: