The first major theme of The Reason for God is that of addressing objections to Christianity. Keller chooses not to frame those objections based on their presentation in the works of the “new atheists”—partly, it would appear, because he thinks that they have already been sufficiently debunked. Instead, he frames the objections to Christianity as they have been presented to him by ordinary people in the course of his pastoral ministry.

As such, the objections Keller is most interested in are not high-level philosophical or scientific concerns but issues that have become commonplace within the popular zeitgeist. He touches on technical aspects of philosophy and science where appropriate, but these are not the central features of his arguments, largely because most of the objections to Christianity he has encountered are not issues that arise from academic research but from encounters with ordinary New Yorkers. Further, he holds that philosophy and science provide ample evidence in favor of Christianity, not against it, and so he deals with objections from those areas in fairly succinct fashion: “Though you could not prove that the fine-tuning of the universe was due to some sort of design, it would be unreasonable to draw the conclusion that it wasn’t” (136).