Charles Haddon Spurgeon once said,
"Perhaps you know the legend, or perhaps true history of the awakening of Augustine. He dreamed that he died, and went to the gates of Heaven, and the keeper of the gates said to him, "Who are you?" And he answered, "I am a Christian." But the porter replied, "No, you are not a Christian, you are a Ciceronian, for your thoughts and studies were most of all directed to the works of Cicero and the classics—and you neglected the teaching of Jesus. We judge men here, by that which most engrossed their thoughts, and you are judged not to be a Christian, but a Ciceronian." When Augustine awoke, he put aside the classics which he had studied, and the eloquence at which he had aimed, and he said, "I will be a Christian!" And from that time he devoted his thoughts to the Word of God, and his pen and his tongue to the instruction of others in the truths of the gospel."
That is a nice story and all, but for anyone who has bothered to actually look at Augustine in the slightest, he/she will know that while he may have "devoted his thoughts to the Word of God, and his pen and his tongue to the instruction of others," it was not in the "truths of the Gospel." Augustine contradicted the very words of Jesus in the Teaching on the Mount. Jesus instructed us to "Love your enemies, do good to those who hate you, bless those who curse you, pray for those who mistreat you. If someone slaps you on one cheek, turn to them the other also." But Augustine taught that it is okay to "return evil for evil" as long as you have love in your heart toward them. Augustine also taught that Christians were allowed to make "holy war" on others. Again, contrary to the teachings of Jesus and His apostles and the early Christians of the first three centuries. A great deal of what Augustine taught was not "truths of the Gospel" in the least. In fact, Augustine was a heretic in several senses of the word. He condemned others as "heretics" who were not nearly the heretic he was.
Many a professing Christian is in no different a boat than Augustine in his dream. They are Augustinians, Lutherans, Calvinists, Mennonites, Wesleyans, Spurgeonites, MacArthurites, Piperites, etc. They pour over and study the works of these men, and their grave errors in interpretation, but they have neglected the teachings of Jesus, His apostles, and the early Christians. They would more accurately be judged not to be Christians but to be named after these men instead because they are their followers rather than Christ's.
If you would like to learn more about Augustine, read this.