"The Catholic Church started in the fourth century, when Emperor Constantine mixed Christianity with Roman paganism." You'll hear this claim in sermons, videos, and comment sections. History tells a very different story.
Short answer: No. Constantine granted Christians religious freedom in 313 and called the Council of Nicaea in 325, but the Church he favored already existed. Christian writers were calling it "the Catholic Church" two centuries before him, and it already had bishops, a weekly Eucharist, and lists of bishops reaching back to the apostles.
Key verses on the founding of the Church
- "upon this rock I will build my church, and the gates of the netherworld shall not prevail against it" (Matthew 16:18)
- "And behold, I am with you always, until the end of the age." (Matthew 28:20)
- "They devoted themselves to the teaching of the apostles and to the communal life, to the breaking of the bread and to the prayers." (Acts 2:42)
- "the holy Spirit has appointed you overseers, in which you tend the church of God" (Acts 20:28)
- "your faith is heralded throughout the world" (Romans 1:8)
Scripture quotations are from the New American Bible, Revised Edition (NABRE), © 2010, 1991, 1986, 1970 Confraternity of Christian Doctrine, Washington, D.C. Used by permission. All rights reserved.
What Catholics Actually Teach
Catholics believe Jesus Christ founded the Church on the apostles. The Catechism says the Church "was, in this fundamental sense, catholic on the day of Pentecost and will always be so until the day of the Parousia" (CCC 830). She is apostolic because she "was and remains built on 'the foundation of the Apostles'" (CCC 857).
What Catholics do not teach:
- That Constantine was a pope or a founder. He was an emperor, and he was not even baptized until shortly before his death in 337.
- That Constantine was a model Christian. Catholics can admit his flaws freely. His legacy is mixed.
- That the Church's doctrines were invented at Nicaea. The council defended what the Church already believed.
The Biblical Case
1. Jesus founded one Church and promised it would last
Jesus said, "upon this rock I will build my church, and the gates of the netherworld shall not prevail against it" (Matthew 16:18). He promised the apostles, "I am with you always, until the end of the age" (Matthew 28:20). If the true Church vanished for nearly three centuries and was replaced by an emperor's creation, those promises failed. (See Was There a Great Apostasy?)
2. The apostolic Church already had a recognizable shape
The first Christians "devoted themselves to the teaching of the apostles and to the communal life, to the breaking of the bread and to the prayers" (Acts 2:42). Doctrine, communion, Eucharist, and liturgical prayer were there from the start, not added in 325.
3. The Church had appointed leaders from the beginning
St. Paul told the presbyters of Ephesus, "the holy Spirit has appointed you overseers, in which you tend the church of God that he acquired with his own blood" (Acts 20:28). St. Paul and St. Barnabas "appointed presbyters for them in each church" (Acts 14:23). St. Paul left St. Titus in Crete to "appoint presbyters in every town" (Titus 1:5). Constantine inherited a Church with ordained leaders; he did not create one.
4. The Church in Rome was famous long before Constantine
Around AD 57 (approximate), St. Paul wrote to the Christians of Rome: "your faith is heralded throughout the world" (Romans 1:8). The Roman church existed more than 250 years before Constantine.
What Actually Happened: A Timeline
Dates before 300 are approximate unless stated.
- c. 96: Pope St. Clement I (St. Clement of Rome) writes to Corinth, explaining that the apostles appointed bishops and deacons and provided for successors.
- Late first or early second century (dating debated): The Didache describes baptism, the Lord's Day Eucharist, and the appointment of "bishops and deacons."
- c. 107–110: St. Ignatius of Antioch writes of bishops, presbyters, and deacons and uses the phrase "the Catholic Church."
- c. 180: St. Irenaeus of Lyons lists the bishops of Rome from the apostles to his own day.
- 250 and 303–311: Empire-wide persecutions under Decius and then Diocletian and his successors. Many Christians die for a faith the state tries to destroy.
- 311: Galerius issues an edict of toleration, ending the persecution in much of the empire.
- 313: Constantine and Licinius agree at Milan to grant religious freedom (the "Edict of Milan").
- 325: Constantine calls the Council of Nicaea to settle the Arian controversy over whether the Son is truly God.
- 337: Constantine is baptized shortly before his death.
- 380 (February): Emperor Theodosius I, with his co-emperors, decrees that all subjects should hold the faith of the bishops of Rome and Alexandria (the Edict of Thessalonica). This, not Constantine's policy, made Nicene Christianity the empire's official faith.
The Edict of Milan did not make Christianity the only religion. Eusebius records its words: "We resolved, that is, to grant both to the Christians and to all men freedom to follow the religion which they choose" (Church History 10.5.4).
Objections Answered
(a) "Nicaea invented the divinity of Jesus."
At its strongest: Some writers, from Jehovah's Witnesses to popular novelists, claim that belief in Jesus as God was voted in at Nicaea under imperial pressure.
Answer: Scripture already calls Jesus God: "the Word was God" (John 1:1), and St. Thomas confessed, "My Lord and my God!" (John 20:28). Around 107–110, St. Ignatius wrote, "For our God, Jesus Christ, was, according to the appointment of God, conceived in the womb by Mary" (Ephesians 18). Nicaea defended an existing faith against Arius, who denied it. Ironically, late in his reign Constantine turned against St. Athanasius, Nicaea's great defender, and sent him into exile (335–336). An emperor who wavered could hardly have dictated the creed. (More: Does John 1:1 Say "a God"?)
(b) "Constantine paganized Christianity, starting with Sunday worship."
At its strongest: Constantine had long honored the sun god, and in 321 he made Sunday a legal day of rest. Critics argue that Sunday worship and other customs entered the Church from Roman paganism through him.
Answer: Start with the New Testament. At Troas, "On the first day of the week when we gathered to break bread," St. Paul preached to the assembly (Acts 20:7). He told the Corinthians to set aside their collection "On the first day of the week" (1 Corinthians 16:2). St. John received his vision "on the Lord’s day" (Revelation 1:10), which the NABRE note explains is Sunday. Sunday worship was apostolic, more than two centuries before Constantine's law of 321.
The earliest Christians after the apostles kept the same day. The Didache says, "But every Lord's day gather yourselves together, and break bread, and give thanksgiving" (ch. 14). St. Ignatius describes believers "no longer observing the Sabbath, but living in the observance of the Lord's Day" (Magnesians 9). The Church honored Sunday because Jesus rose on the first day of the week, not because Constantine did. (More: Should Christians Worship on Saturday or Sunday?)
(c) "Constantine and Nicaea picked the books of the Bible."
At its strongest: This claim is popular online: the emperor and his bishops chose the books that suited them and suppressed the rest.
Answer: The Council of Nicaea's surviving acts are a creed, twenty canons on church discipline, and a synodal decree. None of them lists the books of the Bible (Catholic Encyclopedia, "First Council of Nicaea"). The canon was discerned over centuries, with lists from St. Athanasius (367), the Council of Rome under Pope St. Damasus I (382), and the African councils of the 390s. (More: Who Decided Which Books Are in the Bible?)
The Early Church Agrees
The best answer to the Constantine theory is to read Christians who wrote before him. They read Acts 14 and 20 the Catholic way: the apostles appointed bishops, and those bishops had successors.
- St. Clement of Rome (First Epistle to the Corinthians, c. AD 96, approximate) says the apostles "appointed the first fruits [of their labours]" "to be bishops and deacons of those who should afterwards believe" (42). Knowing "that there would be strife on account of the office of the episcopate," they provided that "other approved men should succeed them in their ministry" (44).
- St. Ignatius of Antioch (Letter to the Smyrnaeans, c. AD 107–110, approximate): "Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever Jesus Christ is, there is the Catholic Church." (ch. 8) In the same letter he warns against those who "abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ" (7). Two centuries before Nicaea, the Catholic Church had a name, bishops, and faith in the Real Presence.
- The Didache (late first or early second century, dating debated): "Therefore, appoint for yourselves bishops and deacons worthy of the Lord, men meek, and not lovers of money, and truthful and proven" (ch. 15).
- St. Irenaeus of Lyons (Against Heresies, c. AD 180), after listing twelve bishops of Rome from Pope St. Linus to Pope St. Eleutherius: "In this order, and by this succession, the ecclesiastical tradition from the apostles, and the preaching of the truth, have come down to us." (3.3.3) Of the Roman church he adds: "For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority" (3.3.2).
Conclusion
Constantine changed the Church's legal situation, not its identity. He ended persecution and called a council, but he did not found the Church, write its creed, choose its Bible, or create its bishops. All of that existed before he was born.
If you have heard that the Catholic Church began with Constantine, read St. Ignatius, the Didache, and St. Irenaeus for yourself. You will meet the Catholic Church, bishops, Eucharist and all, centuries before 313. (For a broader timeline, see Who Founded Your Church?)
Come home. The Church that already had bishops, the Eucharist, and the name Catholic long before Constantine was born still stands today as the Catholic Church. Christ did not found many churches. He founded one, on St. Peter and the apostles (Matthew 16:18), and that Church is the Catholic Church. "It is through Christ's Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained" (CCC 816). If you are a baptized Christian, you already share "a certain, although imperfect, communion" with her (CCC 838). Every truth you already hold is a call to the rest of the way. Christ is calling you into the Catholic Church.
Your next step: Come to Mass this Sunday at your local Catholic church. You can find one near you at MassTimes.org. Everyone is welcome; if you're not yet Catholic, pray with us but don't receive Communion yet. When you're ready to become Catholic, call the parish office and ask about OCIA, the Order of Christian Initiation of Adults. They will walk you through every step. Read our guide: How Do I Become Catholic? Not ready yet? Get our free pocket guide below and keep learning.
FAQ
Did Constantine make Christianity the official religion of Rome? No. He granted Christians freedom and favored the Church. The decree requiring the faith of the bishops of Rome and Alexandria came from Theodosius I in 380.
Was Constantine a Christian? He supported the Church from 312 onward but was baptized only shortly before his death in 337. His personal faith and conduct remain debated.
Did the pope attend the Council of Nicaea? No. Pope St. Sylvester I was represented by two Roman priests.
Sources
Scripture (NABRE, bible.usccb.org): Matthew 16:18; Matthew 28:20; John 1:1; John 20:28; Acts 2:42; Acts 14:23; Acts 20:7, 28; Romans 1:8; 1 Corinthians 16:2; Titus 1:5; Revelation 1:10 (with NABRE note).
Catechism of the Catholic Church (vatican.va): 816; 830; 838; 857.
Church Fathers (newadvent.org): Clement of Rome, 1 Clement 42, 44 (ANF vol. 1); Ignatius of Antioch, Letter to the Smyrnaeans 7–8, Letter to the Ephesians 18, and Letter to the Magnesians 9 (ANF vol. 1); Didache 14–15 (ANF vol. 7); Irenaeus, Against Heresies 3.3.2–3 (ANF vol. 1); Eusebius, Church History 10.5.4 (NPNF2 vol. 1); Eusebius, Life of Constantine 4.61–62 (NPNF2 vol. 1).
Historical background: Catholic Encyclopedia, "First Council of Nicaea"; Catholic Encyclopedia, "Constantine the Great"; Catholic Encyclopedia, "Theodosius I".