Barnabas (d. 61), an apostle according to Acts 14:14, traveled with the apostle Paul and John Mark on several missionary journeys and was martyred for his faith.  Early writers Clement of Alexandria and Origen attributed the Epistle of Barnabas to this apostle; however, the work may have been written after AD 70 by another Barnabas.

Caius (early 3rd century) was a presbyter at Rome who wrote against the heresies of his day.  Only fragments of his works exist today, including Against the Heresy of Artemon and Canon Muratorianus, a summary of several books later included in the New Testament.

Clement of Alexandria (c. 150-215) was raised in paganism but grew disillusioned with its moral depravity and converted to Christianity.  Educated in philosophy and literature, he became a teacher at the catechetical school in Alexandria, Egypt, where Origen was one of his pupils.  Clement’s main works include Protrepticus (The Exhortation to the Heathen, presenting the gospel message to the Greek pagans), Paedagogus (The Instructor, teaching the Christian ethos and its practical applications), and Stromata (Miscellanies, describing the life of the person who truly knows God).

Clement of Rome (35-99) was bishop of the church at Rome.  He likely learned from Peter and Paul, and tradition holds that he is mentioned in Philippians 4:3.  His only surviving work is 1 Clement, an epistle to the Corinthian church that was read at the church alongside Paul’s writings.

Commodianus (2nd century) was a poet from North Africa who converted to Christianity in his later years.  He is known for his Instructions, consisting of 80 acrostic poems discussing the futility of paganism and the essence of the Christian life.

Cyprian (c. 200-258) was bishop of the church at Carthage, North Africa during a time of intense persecution.  He was influenced by Tertullian and died as a martyr at the hands of the Romans. Cyprian wrote several treatises on the third-century church as well as epistles to numerous individuals and churches.

Hermas (2nd century) was the brother of Pius, bishop of the church at Rome, and was likely mentioned by Paul in Romans 16:14.  He wrote The Shepherd of Hermas, consisting of five visions, twelve commandments, and ten parables of practical teachings for the Christian life. The Shepherd was read and revered in churches, and many writers of the early church considered it to be divinely inspired.

Hippolytus (c. 170-236) possibly learned from Irenaeus and served as a presbyter at Rome before dying as a martyr.  He is known for the Refutation of All Heresies, which documents the belief systems of paganism and 33 Gnostic heresies.  He also wrote several commentaries.

Ignatius (35-108) was a disciple of John and bishop of the church at Antioch.  He wrote several letters to area churches while on his way to Rome, where he eventually died as a martyr.  Ignatius documented key points of theology and structure in the New Testament church. The authenticity of some of his works is disputed; however, his epistles to the Ephesians, Magnesians, Trallians, Romans, Philadelphians, Smyrnaeans, and Polycarp are considered authentic.

Irenaeus (c. 130-200) was originally from Smyrna, where he was raised in a Christian family and learned from Polycarp.  Polycarp appointed Irenaeus bishop of the church at Lyons, France, following an intense persecution during which his predecessor, Pothinus, was martyred.  Irenaeus’ most important work is Against Heresies, which was written to combat the teachings of the Gnostics.

Justin Martyr (100-165) was a philosopher who considered the ideas of numerous secular teachers before converting to Christianity.  He was a devoted evangelist and apologist for the Christian faith and was executed in Rome as a martyr.  Justin’s most important works are his two apologies, written to the Roman Emperor and the Senate respectively, in which he outlined the beliefs of the church and the godly lifestyle of true believers.  The first apology is unique in that Justin framed it as a legal document, petitioning the authorities to charge Christians based on any wrongdoing they could find rather than simply because they were Christians, while strongly and clearly presenting the salvation message.

Lactantius (c. 260-325) was an eloquent writer from North Africa who became advisor to Constantine and taught his son Crispus.  The Divine Institutes, written between 303 and 311, was the first full-length work of Christian theology written in Latin.  Lactantius is said to have written with a grace and eloquence reminiscent of Cicero.

Marcus Minucius Felix (d. 260) was a Roman lawyer who became a Christian.  He is known exclusively for Octavius, an apologetic and literary masterpiece recounting a conversation between a Christian and an unbeliever.

Origen (184-253) studied with Clement of Alexandria and succeeded him as teacher at the catechetical school in Alexandria, Egypt.  Later in life, he was ordained as a presbyter in Caesarea, Palestine, before being tortured for his faith and dying as a martyr.  Origen was a prolific writer known for his apologies, theological works, and commentaries on many books of the Bible.  Two of his most notable writings were On the First Principles, the first textbook of systematic theology, and Against Celsus, a defense of Christianity against the pagan philosopher Celsus.

Papias (c. 60-163) was bishop of the church at Hierapolis.  Like Polycarp, Papias learned from the apostle John.  He wrote the five-book set entitled Exposition of the Sayings of the Lord, although only fragments of his works survive today.

Polycarp (69-155) was a personal disciple of the apostle John and was appointed by John to be bishop of the church at Smyrna.  His only surviving work is an epistle to the Philippian church.  A friend of Ignatius and teacher of Irenaeus, Polycarp lived an exemplary life and died as a martyr as recounted in The Martyrdom of Polycarp, a letter sent from the church at Smyrna.

Tertullian (c. 160-230) was a teacher from Carthage, North Africa who wrote numerous apologies, warnings against heresy, and exhortations to believers.  A prolific writer, Tertullian wrote about nearly every possible topic of Christian living as well as several books exposing the heretical teachings of the Gnostics.

Theophilus of Antioch (2nd century) was the sixth bishop of the church at Antioch.  He was born into a pagan family but converted to Christianity after reading the Scriptures.  He wrote several commentaries and defenses against heresy; however, his only surviving works are three books written to convince his friend Autolycus of the superiority of the Christian faith.