What can we know about God by reason alone? Philosophical theology is the attempt to obtain such knowledge. An ancient tradition, which is perhaps more influential now than ever, tries to derive the attributes of God from the principle that God is the greatest possible being. Jeff Speaks argues that that constructive project is a failure. He also argues that the related view that the concept of God is the concept of a greatest possible being is a mistake. In the last chapter, he sketches an alternative path forward.