Augustin's knowledge, when he began to lecture, could not have been very deep, for he had only lately quitted the student's bench himself. His duties forced him to learn what he did not know. In teaching he taught himself. It was at this time that he did most of the reading which afterwards added substance to his polemics and treatises. He tells us himself that he read in those days all that he could lay hands on. He is very proud of having read by himself and understood without any assistance from a master, the _Ten Categories_ of Aristotle, which was considered one of the most abstruse works of the Stagirite. In an age when instruction was principally by word of mouth, and books comparatively rare, it is obvious that Augustin was not what we call an "all-devouring reader." We do not know if Carthage had many libraries, or what the libraries were worth. It is no less true that the author of _The City of God_ is the last of the Latin writers who had a really all-round knowledge. It is he who is the link between modern times and pagan antiquity. The Middle Age hardly knew classical literature, save by the allusions and quotations of Augustin.
So in spite of family and professional cares, he did not lose his intellectual proclivities. The conquest of truth remained always his great ambition. He still hoped to find it in Manicheeism, but he began to think that it was a long time coming. The leaders of the sect could not have trusted him thoroughly. They feared his acute and subtle mind, so quick to detect the flaw in a thesis or argument. That is why they postponed his initiation into their secret doctrines. Augustin remained a simple _auditor_ in their Church. By way of appeasing the enormous activity of his intelligence, they turned him on to controversy, and the critical discussion of the Scriptures. Giving themselves out for Christians, they adopted a part of them, and flung aside as interpolated or forged all that was not in tune with their theology. Augustin, as we know, triumphed in disputes of this kind, and was vain because he excelled in them.
And when he grew tired of this negative criticism and asked his evangelists to give him more substantial food, they put him on some exoteric doctrine calculated to appeal to a young imagination by its poetic or philosophical colouring. The catechumen was not satisfied, but he put up with it for lack of anything better. Very prettily he compares these enemies of the Scriptures to the snarers of birds, who defile or fill with earth all the water-places where the birds use to drink, save one mere; and about this they set their snares. The birds all fly there, not because the water is better, but because there is no other water, and they know not where else to go and drink. So Augustin, not knowing where to quench his thirst for truth, was fain to make the best of the confused pantheism of the Manichees.