  When he read “the books of the Platonists,” Augustine opened up three routes to proving the existence of God, though he himself explored only one. Arguments like Aristotle’s that begin in the world must proceed from effect to cause and have been called cosmological arguments, though aitiological—meaning simply an argument uncovering causes—seems a better description. When Augustine turned within his mind he opened up two other routes to God. The second route also proceeds from effect to cause, but starts within the mind and searches out God as the ultimate cause of the mind’s knowledge.  This is the illumination argument for God. Augustine’s turn inward also opened up a third route, later given by Kant the unhappy name of ontological argument. The fullest development of this neoplatonic approach to God stood ready to be realized, when all three routes, the aitiological, illuminationist, and ontological, would be scouted out by one and the same philosophical mind. That mind was not Augustine’s or Anselm’s but Bonaventure’s.