 What has yet to be dealt with, clearly, is Mersenne’s problem above—(C), that the real possibility of a most perfect being cannot be demonstrated. Leibniz offers several types of arguments against this. One relies on the fact that other things are clearly possible, together with the claim that only a necessary being provides a satisfactory ground or explanation for the possible existence of contingent beings. So on the assumption that contingent beings possibly exist, it must be at least possible for God, as a necessary being, to exist (for more on this kind of argument from possibility, see section 2.3 below). 