 The most significant disagreement, however, is again the one that Mersenne raised against Descartes. How can the claim about metaphysical possibility in (1) be justified? Adams (1994: ch.8), following Leibniz, claims that we are rationally permitted, in the absence of strong reasons to the contrary, to presume the real possibility of most things, including God. Others argue that no such presumption of metaphysical possibility is justified, especially regarding supersensible things.