 A third problem, raised in the Second Objections by Father Marin Mersenne, is that the argument would be sound only if a maximally perfect being is really possible, or, equivalently, only if there is a genuine divine essence. But this, Mersenne complains, has not been established (AT 7.127). (Side note: Gaunilo and Mersenne are good examples of how devout theists might still take issue with natural theological efforts to prove God’s existence.)