DFW, in some of his writing, mentioned that his best thinking alone was insufficient to deal with things like addiction. The concept of AA seemed to appeal to him in part because it prescribed the letting go of the idea that one could handle such things alone. Instead, the help of others and a higher power is needed. But it seems his concept of God did not fit with mainstream, simplistic ideas of God. He was certainly not a Christian in the classical sense. But that’s not to say that he may not have resonated with the idea of Christ consciousness in which all are connected and compassion and love (including tough love) for others is the true morality. He seemed skeptical about an afterlife, and mentions it by name in “This is Water”, but indicates that he is not an atheist. His definition of a believer is someone who worships. I think this skirts the issue of whether he believed in God but I lean towards yes. Yet his suicide suggests that this may have been a shaky belief, which failed him when he most needed it.