What’s the Difference Between Catholics, Orthodox and Protestants?

The short answer: All three are Christian traditions that confess one God in three Persons, and Jesus as fully God and fully man, crucified and risen. They differ on serious questions: where final authority lies, how a person is made right with God, Mary and the saints, communion and the pope. Evangelicals themselves differ on how to regard Catholic and Orthodox Christians, and this chapter sets out the differences fairly without mocking anyone.

Maybe your best friend is Catholic and goes to Mass. Maybe you’ve walked into an Orthodox church full of icons and candles. Maybe you’ve heard someone say Catholics “aren’t real Christians”, and someone else say the differences don’t matter at all. This is a question where facts matter and where Christians disagree, so here’s both.

Where they agree

Catholics (about half the world’s Christians), Orthodox and Protestants all confess the ancient creeds, like the Nicene Creed. They agree that there is one God, Father, Son and Holy Spirit; that Jesus is God the Son, born of the Virgin Mary; that He “died for our sins according to the Scriptures, that He was buried, that He was raised on the third day” (1 Corinthians 15:3–4); that He will come again; and that the Bible is God’s Word. That shared core is huge.

How the split happened

For about a thousand years, Christians in East and West mostly belonged to one church, though with growing tensions. In 1054, the Eastern (Orthodox) and Western (Catholic) churches split, partly over the authority of the bishop of Rome. Then, in 1517, a German monk called Martin Luther challenged the sale of indulgences, and the Protestant Reformation began. It was mainly an argument about how a sinner is made right with God and about the authority of Scripture. The Catholic Church responded with reforms of its own, and the divisions remained.

The main differences

• Authority. Catholics hold that God speaks through Scripture and Tradition, interpreted by the Church’s teaching office under the pope. Orthodox Christians hold Scripture within Holy Tradition, especially the ancient councils. Protestants hold that Scripture is the final authority over every tradition, though they value the creeds.
• Salvation. All three say salvation is by God’s grace in Christ. Catholics teach that God’s grace, received through faith and the sacraments, makes a person righteous over a lifetime. Orthodox Christians often describe salvation as healing and growing union with God. Protestants teach that a person is “justified by faith in Christ and not by works of the law” (Galatians 2:16): declared right with God by trusting Christ alone, with good works following as the fruit.
• Mary and the saints. Catholics and Orthodox honour Mary highly and ask her and the saints to pray for them, insisting this is not worship. Protestants honour Mary as a model of faith, who said, “all generations will call me blessed” (Luke 1:48), but pray directly to God, stressing that “there is one mediator between God and men, the man Christ Jesus” (1 Timothy 2:5).
• Communion. Catholics believe the bread and wine become Christ’s body and blood; Orthodox believe in a real change without defining how; Protestants hold a range of views. (Book 2 answered what communion is for.)
• The pope. Catholics see the pope as Peter’s successor and head of the Church on earth, pointing to Jesus’ words, “you are Peter, and on this rock I will build My church” (Matthew 16:18). Orthodox and Protestants read that verse differently and don’t accept his authority.

How evangelicals regard them

Here evangelicals genuinely differ. Some warmly regard believing Catholics and Orthodox as brothers and sisters in Christ, while disagreeing on important points. Others are more cautious, believing that official teaching on salvation, Mary or the saints can obscure the gospel of grace. Almost all agree on two things: no one is saved by a church label, Protestant or otherwise, but by trusting Christ; and individual Catholics and Orthodox can certainly know and love Him. This book won’t decide between those views.

How to talk about it

Never mock someone’s church. Learn what your Catholic or Orthodox friends actually believe, from them. Jesus prayed “that all of them may be one” (John 17:21). Talk about your differences honestly and kindly, and you may find you share more than you expected.

Think about it: Do you know what your own church believes about these questions, and why? What could you learn from a friend in another tradition?

Go deeper: The Key Teachings of C. S. Lewis — Lewis, an Anglican, pictured “mere Christianity” as a great hall with doors into many rooms: you must choose a room because you believe its teaching true, and then be kind to those who chose other doors. Before publishing one series of his famous talks, he checked the script with an Anglican, a Methodist, a Presbyterian and a Roman Catholic. Start with chapter 6, “The Faith Held in Common”.