Still another heresy was beginning to poison religious thought: Arianism, or the denial of the divinity of Jesus Christ, was invading the church of Africa. And the writings of St. Augustine against this movement are among his most luminous and brilliant works. He wrote three letters and fifteen books on the Trinity--these he commenced in 400 and completed in 416. Perhaps the clearest and plainest are the one hundred and twenty-four treatises (so called) on the Gospel of St. John, and ten on the First Epistle of the same Apostle. They were sermons or catechetical instructions and homilies, delivered during the year 416 to his flock, on the prevalent heresies but especially on the Arian. And his response to the five questions of Honorius, a citizen of Carthage, contains lucid expositions of some difficult portions of Scripture.
On Scripture matters, besides the works just mentioned, St. Augustine's enlightened views are found in twelve books on the "Literal Sense of Genesis;" in these he seems to have divined all modern objections and theories about this work of Moses. On the seven first books of the Bible, he has left us seven treatises. "An Explanation of the Psalms," a correspondence with St. Jerome on the Epistle to the Galatians, four books on the agreement of the Evangelists, two on Gospel questions, and a book on "Things That are not Seen," should not be unknown to Biblical students.
Nor was the Pagan attitude toward Catholic Truth forgotten. He had passed through the phase, and knew the Pagan mind. He put down their difficulties, reasoned away their doubts, threw light on their darkness, led them on in truth, in "The True Religion," "Eighty-three Questions," "The Christian Doctrine," and an early treatise on the "Immortality of the Soul."
But by far his greatest and most enduring works are his "Confessions" and "The City of God." The former, at once a poem, a history, and a treatise of philosophy, beautifully expresses the trials and efforts of a human soul striving for truth and happiness away from God, and the ecstatic sentiments of the same soul on the attainment of both truth and happiness in the faith and virtues of Jesus Christ and in His Gospel. The other, in eloquent and philosophical vein, discourses on the Church of God on earth and in heaven; shows the hollowness of all opinions, thoughts, and efforts contrary to the eternal order which is God; is, as it were, an encyclopedia of all that he had written before, an exhaustless summary of refutation against heresy and paganism, and an analysis of the glories and benefits of Christianity. St. Augustine in its composition occupied all the time from 413 to 426--the period of his momentous struggle against Pelagianism.