The second-century date refers to Marcion’s attempt to compose a canon of Scripture in conformity to his anti-Jewish bias, which contained only a version of the Gospel of Luke, ten letters of Paul and his own work titled “Antitheses.” Marcion taught that the God of Jesus was not the same as the God of the Hebrew Scriptures, and that in fact the God of the Hebrews should be rejected. But it was Marcion who was rejected by the church in Rome beginning during his lifetime in the second century C.E. With the leadership of Irenaeus and Tertullian, the early church of the second and third centuries rose to the challenge, and with Augustine in the fourth century the issue was finally settled. See Childs, Old Testament as Scripture, p. 42; and John J. Clabeaux, “Marcion,” Anchor Bible Dictionary (ABD) (Garden City, NY: Doubleday, 1992), vol. 4, pp. 514–516.