Quintus Septimius Florens Tertullianus, more commonly known as Tertullian of Carthage, was a prolific Christian writer, activist, and apologist of the late second century who took part in the issues of doctrine debated during the early years of Christianity. His works provide us with some of the best witnesses in the West of Orthodox Christian thinking and practices of the time. He helped establish Latin as an ecclesiastical language, paralleling that of Greek. During his early years he denounced doctrines considered heretical at the time, but in the latter apart of his life he began to adopt views that were considered schismatic if not heretical themselves. Thus, while having contributed much to defining Orthodoxy, he ended his life leading his own sect after have joining the Montanist movement.
What little is known of Tertullian's life is from references in his writings and from the writings of Eusebius of Caesarea and Jerome, who wrote in the 4th century. Tertullian was born about the year 155 in Carthage in North Africa into a pagan family. His father is believed to have been a centurion or aide de camp in the Roman army in Africa. He was educated in Carthage that was noted as a home of orators. He was knowledgeable in Greek as well as Latin. Although the works are no longer available today, he notes in his own writings his authorship of three books written in Greek. Being scholarly and in such an educated environment he received a very good education, studying mainly jurisprudence. By profession he appears to have been an advocate in the law courts of Rome. Apparently, he was a pagan until mid life. He was a married man, evidenced by letters to his wife. It was while in Rome that he became interested in Christianity, but became active after returning to Carthage. He apparently was impressed by Christian beliefs and ideals such as the moral attitudes of Christians and strong belief in one God.
Tertullian became a Christian about 197 and soon became a leader in the church in North Africa. It is believed his conversion was sudden. This belief is based on the images of Christian life that he presents in his writings. Some believe he became a priest, probably about the year 200, in the church in Carthage.
About 207, he turned to Montanism, a schismatic sect, leaving the mainline Orthodox church. Apparently he was influenced by the sect's stringent moralism, and he was an active exponent of the schism, becoming a leader of the sect in Carthage. His secession from Orthodoxy is cloudy. Some view that his departure may have been forced after the Bishop of Rome disapproved of Montanism, resulting in the excommunication in Carthage of many of the most ardent Montanists.
Regardless of his schism, Tertullian continued to fight the heresies, particularly Gnosticism. His doctrinal works were influential on Cyprian. In time he found the Montanists not rigorous enough. So he founded his own group, the Tertullianists, which as group continued to exist in North Africa until the 5th century. His latest writings date to no later than 220. The date of his death is not known, but Jerome noted that he lived to an old age.
The period for which extant writings are available begins with apologetics written in 197 and continue until 220. He apparently joined the Montanists in 206, and separated himself from the Orthodox about 212. In addition to fragments of some of his works, thirty one of his works are extant. About fifteen other works are no longer available. His writings can be grouped into two sets, the first including apologetics and polemic writings, and the second, other writings that consider practical and disciplinary matters. His earliest works begins with the piece "To the Martyrs" and then continue with two works, "Ad nationes" and "Apologeticus", that appear to cover the same material but apparently for different reasons. These apologetic works put forward barbed defenses of Christianity and Christians against the rebukes from the pagans. In these Tertullian sets out the principle of religious freedom and that Christians must be given fair trials based on facts before they are condemned to death. He contested the stories of the pagans, such as claims of child sacrificing by providing testimony of Pliny that Christians do not commit murder, adultery, and such crimes. Also, he drew parallels of accusations made by the pagans of Christians to the same deeds as part of the pagan religion.
He also expounded on heresies and heretics, refuting their arguments and maintaining the continuity of teachings from Christ through the Apostles. His writings include works of instruction for catechumens, laying out the life styles for the Christians. He wrote much on penance, an issue that may have been part of his move to Montanism. A major product among his works are five books arguing against the heretic Marcion. His discussions of the nature of the Holy Trinity are among the earliest expressions of the controversies that would be settled over the following centuries.