In the first book of our answer to the work of Celsus, who had boastfully entitled the treatise which he had composed against us A True Discourse, we have gone through, as you enjoined, my faithful Ambrosius, to the best of our ability, his preface, and the parts immediately following it, testing each one of his assertions as we went along, until we finished with the tirade of this Jew of his, feigned to have been delivered against Jesus. And in the second book we met, as we best could, all the charges contained in the invective of the said Jew, which were levelled at us who are believers in God through Christ; and now we enter upon this third division of our discourse, in which our object is to refute the allegations which he makes in his own person.
He gives it as his opinion, that “the controversy between Jews and Christians is a most foolish one,” and asserts that “the discussions which we have with each other regarding Christ differ in no respect from what is called in the proverb, 'a fight about the shadow of an ass.'” and thinks that “there is nothing of importance in the investigations of the Jews and Christians: for both believe that it was predicted by the Divine Spirit that one was to come as a Saviour to the human race, but do not yet agree on the point whether the person predicted has actually come or not.” For we Christians, indeed, have believed in Jesus, as He who came according to the predictions of the prophets. But the majority of the Jews are so far from believing in Him, that those of them who lived at the time of His coming conspired against Him; and those of the present day, approving of what the Jews of former times dared to do against Him, speak evil of Him, asserting that it was by means of sorcery that he passed himself off for Him who was predicted by the prophets as the One who was to come, and who was called, agreeably to the traditions of the Jews, the Christ.
Source: Against Celsus (New Advent)