Irenæus, I. c. xxvii. says that Cerdo taught that the God of the Law and the Prophets was not the Father of our Lord Jesus Christ:  for that He is known, but the other unknown, and the one is just, but the other good.  Also III. c. 25, § 3:  “Marcion himself, therefore, by dividing God into two, and calling the one good, and the other judicial, on both sides puts an end to Deity.”  Compare Tertullian, c. Marcion. I. 2, and 6; Origen, c. Cels. iv. 54.