  While Anselm thought this conclusion rules out even the possibility of atheism, Bonaventure more realistically shows how atheism is possible. The problem is with our defective knowledge of God’s nature. Error there can lead by logical inference to the conclusion that God does not exist in the first place. We are spontaneously theists, but can convince ourselves to become atheists. Inadequate definition of God points to a second problem. Knowing God exists is similar to knowing axioms because both are recognized by all.  The difference is that we are quite certain “the whole is greater than the part,” because the terms involved in this axiom are so familiar to us; but about God’s existence we have more an opinion than certain knowledge, because we lack an adequate definition of God’s nature.