Pastor Thabiti Anyabwile draws upon his experience as someone who formerly practiced Islam to respond to Volf's arguments and efforts to clarify Christian views for Muslims who often misrepresent such doctrines as the Trinity.
Contrary to my opening question in the video, Volf does not explicitly state in the book that someone can be both 100 percent Christian and 100 percent Muslim. Rather, he argues more narrowly that you can practice Islam and be 100 percent Christian. He explained in the comments section following TGC's review of his book:
As I see it, to be a Christian (spiritually and not merely culturally), means to accept that Jesus Christ is the final revelation of God. A Christian cannot accept therefore that Muhammad is the Seal of the Prophets. The vast majority of Muslims do not believe that in Jesus Christ is God dwelled in human flesh, for me an essential Christian belief. In the book I state explicitly and precisely how what the publisher put on the book jacket (namely that you can be a practicing Muslim and 100 percent Christian) should be understood. I say: "In holding many Muslim convictions and engaging in many Muslim practices, you can still be 100 Christian." . . . I say that one can be a 100 percent Christian, and engage in some specifically Muslim practices. I explicitly state that I leave open the question whether such person can be described as 100 percent Muslim. That's not on me to decide; Muslims must decide that.