Who is St. Irenaeus, an ancient martyr but new doctor of the church?

(OSV News) -- On June 28, the church celebrates the feast day of St. Irenaeus of Lyon, the most recently declared doctor of the church. Biographical information for St. Irenaeus is rather limited. In fact, few primary sources on him remain at all -- for instance, the only complete texts of his writings exist today by way of later translations.

Irenaeus was born around 130 in the Greek-speaking East. It is most likely that Irenaeus came from Smyrna, on the western edge of what is now Turkey. That was also the city of St. Polycarp, a mentor with whom Irenaeus had been associated from a young age.

It was through the martyr Polycarp -- himself revered and respected as a figure of authority in the early church -- that Irenaeus was acquainted directly with the apostolic age, particularly through his mentor's connection to St. John the Apostle.

Irenaeus was born at a time of growing conversion throughout the Roman Empire, although he was himself born into a Christian family. He spent time studying in Rome, most likely a student of St. Justin Martyr.

Irenaeus is remembered most of all for having lived in the Gaul region of the Roman Empire, which encompassed a large part of today's western Europe, including all of present-day France. Irenaeus made his home and exercised ministry in what is now Lyon -- then called Ludugunum -- which was at the time the largest city north of the Alps. Lyon was not only a population hub then, but it also served as a civic and cultural center. Its population growth was owed to an influx of immigrants, which included Irenaeus himself.

Irenaeus arrived there as a missionary -- according to tradition, sent at the direction of Polycarp -- to help solidify ecclesial life in that blossoming part of the empire. Toward the late 170s, Irenaeus was a presbyter, or priest, and was held in esteem within the local church.

In 177, Irenaeus was dispatched to Rome -- by a group of soon-to-be martyrs held captive and awaiting execution -- to deliver a letter to Pope Eleutherius. The letter -- which expressed, among other things, concern about emerging threats to the unity of faith emerging in the early church -- exists as the first historical evidence of Irenaeus.

Just as Christ prayed before his death that the church might be one, so too did these early Lyonese martyrs. And Irenaeus -- whose very name means "peace" -- served as an emissary of peace and unity by allowing their message to be heard in Rome. It was most likely this trip abroad that spared him from being martyred with Lyon's first bishop, St. Pothinus, and his companions.

Upon his return from Rome, Irenaeus succeeded the martyred Pothinus as bishop of Lyon. Overseeing the rebuilding of the ecclesial life in the city in the wake of persecution and martyrdom, Irenaeus brought to his flock hope and assurance in God's providence.

Most of what remains known of Irenaeus' episcopal ministry, though, is his clear and systematic teaching of the faith. And that seems fitting, especially since he regarded a bishop, above all other functions, primarily as a teacher. Irenaeus helped develop the concept of apostolic succession -- a theme important culturally at the time in fields such as medicine and philosophy.

This helped to solidify the ministry of the bishop in the early church and underscored the bishop's authority in handing on the church's apostolic teaching. An example of his contribution to elevate esteem for the Roman see, Irenaeus provided one of the earliest lists of the first bishops of Rome. Given his ties to St. John the Apostle, Irenaeus served as a credible, public witness to the apostolic testimony.

Aside from a few letters, most of what survives from St. Irenaeus' teachings composes a collection of books titled "Against Heresies," written around 180. This seminal contribution to the church's theological treasury has been esteemed by the famous 20th-century theologian Hans Urs von Balthasar as the "birth of Christian theology."

As a pastor, Irenaeus engaged the culture, and attuned himself to the struggles and difficulties in the lives of those in his flock and the society in which he lived. And, as a bishop, Irenaeus was concerned about ecclesial unity, which meant he had utmost concern to ensure that the apostolic faith was handed on intact and with authenticity.

Irenaeus is now the first pre-Nicene Doctor of the church, since his tenure as a bishop was more than a century before the all-important Council of Nicea, which itself paved the way for codification of Christian dogma and settled various questions and divisions that arose among Christians related to the Trinity and Christ in accord with divine revelation. But even in his own time, Irenaeus saw various threats to the integrity of the Faith emerge.

And so, in his era and in his own ministry, the church began to articulate between orthodoxy and heresy, as the age of the apostles gave way to a new generation of leaders tasked to carry on their ministry. Irenaeus acutely understood the need to counteract the teachings of other leaders who promoted thoughts and ideas -- and attracted followers -- that posed a threat to the apostles' teaching.

Irenaeus' dissident adversaries, for the most part, are collectively known as Gnostics, people who believed that salvation came through obtaining knowledge that existed outside of revelation or might have even contradicted it. Gnostics propose a faith that relies not on objectivity, but subjectivity, where the truth is not the arbiter of one's life or salvation.

More widely known among the targets of Irenaeus' writing was Valentinus (c. 100-180), a disgruntled priest who formed his own community after being passed over for an episcopal appointment. He allegedly claimed to have secret knowledge passed on from St. Paul himself -- which inherently misrepresented and compromised the church's faith -- and argued that salvation was attainable in various degrees.

Irenaeus also responded to other heretics such as Marcion (85-160), whose teaching distorted who Christ is and erroneously proposed that the God of the New Testament was not the same as the Old Testament. Marcion also maintained that St. Paul was the only true apostle of Christ.

In order to dispel such errors, Irenaeus had studied the enemies of such true faith and understood their positions well. He was clever, witty and exhaustive in his rebuttals. He exhibited no interest in dialogue as much as in explaining the faith, desiring only to offer clear refutation of what the Gnostics proposed.

Irenaeus's writing was thorough, grounded in strong philosophical reasoning and saturated with Scripture. His "Against Heresies" presented, in the face of the Gnostics who distorted it, a defense of who Christ is, what Christ revealed and, in accord, what the apostles preached. He combatted Gnostic dualism -- a division between God and the world -- through his articulation of the integrity and coherency of creation.

And the themes of John's Gospel imbue Irenaeus' writings. Irenaeus had a clear, unambiguous devotion to and understanding of the Word, and he was one of the first to put forth the inclusion of four Gospels in the New Testament. He solidified the nascent church's robust Eucharistic faith, articulated the centrality for Christian faith of the church and the episcopal office, and often highlighted the singular importance of Mary.

By thoroughly, comprehensively and coherently defending the deposit of the Faith, Irenaeus had done more than anyone up to that time to secure peace and unity for the church by laying bare those who threatened it through their deviations from the deposit of the faith.

St. Irenaeus' refutation of the Gnostics remains as important today as it was in his own age. In his 2018 apostolic exhortation "Gaudete et Exsultate" ("Rejoice and Be Glad"), Pope Francis warned that, although ancient, gnosticism plagues us still today. He wrote: "Gnostics think that their explanations can make the entirety of the faith and the Gospel perfectly comprehensible. They absolutize their own theories and force others to submit to their way of thinking. A healthy and humble use of reason in order to reflect on the theological and moral teaching of the Gospel is one thing. It is another to reduce Jesus' teaching to a cold and harsh logic that seeks to dominate everything."

Each generation tends to see new manifestations of Gnosticism, our own not excluded, which makes St. Irenaeus' declaration as a doctor of the church in 2022 particularly relevant. Modern Gnostic tendencies give rise to various forms of ecclesial disunity and wreak havoc in society, such as the contemporary promotion of a confused and distorted vision of the human person, evidenced in the ever-emerging dualist competition between the body and the self that is found in modern gender ideology.

St. Irenaeus, however, was given the title the "doctor of unity," which recognizes his contribution to his time and makes him a model for ours.