  Bonaventure was the first thirteenth-century thinker to pay serious attention to the ontological argument. He read the Proslogion of Anselm through Aristotelian lenses. Now Aristotle had recognized three different kinds of scientific principles: common axioms governing all thought, so well known that no one can deny them, and proper principles limited in range to a given science–its definitions and postulates. Anselm seemed to mean that God’s existence is an axiom of thought known by all humans, and Bonaventure agrees: “since our intellect is never deficient in knowing about God if it is, so it cannot be ignorant of God’s existence, absolutely speaking, nor even think God does not  exist.”[52]