After providing reasons for his conversion to theism, Lewis goes over rival conceptions of God to Christianity. Pantheism, he argues, is incoherent, and atheism too simple. Eventually he arrives at Jesus Christ, and invokes a well-known argument now known as "Lewis's trilemma". Lewis, arguing that Jesus was claiming to be God, uses logic to advance three possibilities: either he really was God, was deliberately lying, or was not God but thought himself to be (which would make him delusional and likely insane). The book goes on to say that the latter two possibilities are not consistent with Jesus' character and it was most likely that he was being truthful.