Marvin Cowan discusses the claims surrounding the Book of Mormon, emphasizing that while it is presented as a second witness to the Bible, it lacks the historical and doctrinal consistency found in the Bible. He argues that the Book of Mormon does not provide new revelations or doctrines that are not already established in the Bible, and questions the necessity of its existence if it does not add to the fullness of the gospel. Cowan highlights contradictions within the Book of Mormon and critiques the claims of its divine origin, suggesting that it has been altered over time and lacks archaeological support. He concludes that the Bible, with its numerous witnesses and established teachings, stands as the complete word of God, making the Book of Mormon unnecessary.