In this chapter Keller picks a few "very good arguments for the existence of God" from a lecture given by Alvin Plantiga entitled "Two Dozen (or so) Theistic Arguments." One argument he gives is that the Big Bang indicates that the universe had an origin and is contingent, meaning it has a cause outside itself. Another argument he explains is the fine tuning of the universe. He also finds the regularity of nature as well as our experience of beauty, love and longing for the transcendent to be clues of God. Finally, Keller says that another clue for God is the fact that natural selection cannot be used to explain why we believe in God. If we use natural selection to explain how our brain works as well as the reasoning process, we are admitting that reason itself only exists, like religion, because it helped us survive and that it does not stand independently on its own merits. We, cannot, then, trust our faculties to arrive at a rational argument for natural selection.
These are some of the primary reasons that I do continue to believe in God. I am interested in following up on the lecture by Plantiga cited by Keller.