One of the big questions that as human we face even if we claim to believe in a supreme being. Unless you have some kind of personal awakening that gives you definitive proof that God exist then how can you prove it. Anything we approach in terms of proof is neither here nor there.
Because Mr. Gray does not believe in a higher power, it is difficult engage him in a serious discussion of God. People come to believe in a Creative power or source through faith. If one is living a conscious life it will be hard to deny that we are only flesh. There is more to the human being. Our ability to comprehend and imagine set us apart, our ability to create things visible from an invisible world in phenomenal. Anything we see in the material world comes from the world of spirit or imagination and then made manifest. So, we are not merely flesh we are more.
Dr. Gray states that Hindus, Chinese, Dao and other old religions do not believe in God but he is wrong. All these religions have a basis in one universal creator. He may not have done his research properly. because if he did he would know that Hindus in spite of their complicated rituals and rites do have an underlying belief in a universal God. Ask any Pandit to explain basic Hinduism and he will tell you.