Bishop of Antioch from 169, according to the historian Eusebius was the sixth bishop of the city.   He wrote the famous apologetic work against pagans “Three books ad Autolycus”. Theophilus was a writer with a good education and gumption, his style is simple and elegant. His theology had a serious effect on downstream theologians. He makes no reference to his office in his existing writings, nor is any other fact in his life recorded.      

    Eusebius, however, speaks of the zeal which he and the other chief shepherds displayed in driving away the heretics who were attacking Christ's flock, with special mention of his work Against Marcion. Eusebius and Jerome mention numerous works of Theophilus:

-  Ad Autolycus

-  Against the heresy of Hermogenes

-  Against Marcion

-  Some catechetical writings

  Greek philosophers and poets were for Theophilus, foreigners, that who missed in their trying, but accepts the same ability to reach the truth. Appreciates the Sibyl.

   The "Ad Autolychum", the only extant writing of Theophilus, is an apology for Christianity. It consists of three books, really separate works written at different times. The author speaks of himself as a convert from heathenism. He treats of such subjects as the Christian idea of God, the Scripture accounts of the origin of man and the world as compared with pagan myths. On several occasions he refers (in connection with the early chapters of Genesis) to an historical work composed by him.

   Autolycus, a man of great learning and an earnest seeker after truth, of the divine authority of the Christian religion, while at the same time he exhibits the falsehood and absurdity of paganism. His arguments, drawn almost entirely from Old Testament, are largely chronological. He makes the truth of Christianity depend on his demonstration that the books of Old Testament was long anterior to the writings of the Greeks and was divinely inspired.

   He contrasts the account of the creation of the universe and of man, on which, together with the history contained in the earlier chapters of Genesis, he comments at great length the statements of Plato, of Aratus and other Greek writers on whom he pours contempt.

   It seems that found internal evidence, in the reference to existing persecutions and a supposed reference to Origen and his followers, for assigning the work to a younger Theophilus who perished in the reign of Severus.