Marcion’s Bible rejected the Old Testament with its heroes and prophets; they had been deceived by the Creator, he believed. He also rejected all New Testament references that suggested the Creator and the loving God were the same. In the end, his Bible included only the Gospel of Luke and some letters of Paul. Two hundred years later, the sect was nearly extinct. But it had prodded the church to begin defining what Christians should believe and what books should be called the Word of God.