Certainly, commonplace human reasons can neither bring about nor account for a sincere conversion. Conversion is a divine work. But human reasons, arranged by a mysterious Will with regard to this work, may at least prepare a soul for it. Anyhow, it cannot be neglected that Augustin, coming to Milan full of ambitious plans, there saw Catholicism treated with so much importance in the person of Ambrose. This religion, which till then he had despised, now appeared to him as a triumphant religion worth serving.
But though such considerations might attract Augustin's attention, they took no hold on his conscience. It was well enough for an intriguer about the Court to get converted from self-interest. As for him, he wanted all or nothing; the chief good in his eyes was certainty and truth. He scarcely believed in this any longer, and surely had no hope of finding it among the Catholics; but still he went to hear Ambrose's sermons. He went in the first place as a critic of language, with the rather jealous curiosity of the trained man who watches how another man does it. He wanted to judge himself if the sacred orator was as good as his reputation. The firm and substantial eloquence of this former official, this statesman who was more than anything a man of action, immediately got control of the frivolous rhetorician. To be sure, he did not find in Ambrose's sermons the exhilaration or the verbal caress which had captivated him in those of Faustus the Manichean; but yet they had a persuasive grace which held him. Augustin heard the bishop with pleasure. Still, if he liked to hear him talk, he remained contemptuous of the doctrine he preached.
Then, little by little, this doctrine forced itself on his meditations: he perceived that it was more serious than he had thought hitherto, or, at least, that it could be defended. Ambrose had started in Italy the exegetical methods of the Orientals. He discovered in Scripture allegorical meanings, sometimes edifying, sometimes deep, always satisfying for a reasonable mind. Augustin, who was inclined to subtilty, much relished these explanations which, if ingenious, were often forced. The Bible no longer seemed to him so absurd. Finally, the immoralities which the Manichees made such a great point of against the Holy Writ, were justified, according to Ambrose, by historical considerations: what God did not allow to-day, He allowed formerly by reason of the conditions of existence. However, though the Bible might be neither absurd nor contrary to morals, this did not prove that it was true. Augustin found no outlet for his doubts.