Christianity and Roman Catholicism: What Christians Must Know

Most Roman Catholics and most evangelical Christians use the same words. They say "grace." They say "faith." They say "justification." But they do not mean the same things. And because they do not mean the same things, the difference between the two systems is not a matter of style or preference. It is a matter of the gospel itself.

If you love a Roman Catholic family member, neighbor, or friend, you owe it to them to understand these differences clearly. And if you are a Roman Catholic reading this article, I would ask only that you measure everything here against what the Bible actually says. That is all any of us should do.

What Are the Most Important Differences Between Christianity and Roman Catholicism?

Before we look at specific questions, we need to lay a foundation. There are six areas where Protestant Christianity and Roman Catholicism differ so sharply that they cannot both be right. These are not secondary issues. They touch the very heart of how a person is saved.

1. The Authority of Scripture.

The Protestant Reformation was sparked by a question that historians call the formal cause of the Reformation: Where does authority rest? Protestants hold to sola Scriptura, the conviction that the Bible is the final, ultimate, and only infallible authority for the Christian. Rome teaches a dual-source theory of revelation, claiming that the truth of God is found in both the written Scriptures and the unwritten traditions of the church. Rome also includes the Apocrypha in its Bible, books that Protestants reject as uninspired. And Rome condemns the Protestant doctrine of private interpretation, insisting that the Roman Catholic Church alone has the right to judge the true meaning of Scripture.

2. The Doctrine of Justification.

This is the material cause of the Reformation, the core issue that fractured Christendom in the sixteenth century. Protestants believe in justification by faith alone. The righteousness of Christ is imputed, or legally credited, to the believer's account. God declares the sinner righteous based on the "alien righteousness" of Christ, not on anything inherent within the person. The Protestant formula is: faith equals justification plus works. Works are the fruit of salvation, not the root.

Rome teaches an entirely different framework. In the Catholic system, righteousness is infused into the soul, primarily through baptism. Faith is necessary but not sufficient. Good works and participation in the sacraments are required to merit eternal life. The Roman Catholic formula is: faith plus works equals justification. If a Catholic commits a mortal sin, they lose the grace of justification and must be restored through the sacrament of penance, which requires them to perform works of satisfaction to earn what Rome calls "congruous merit."

3. Sacerdotalism and the Sacraments.

The Roman Catholic Church operates on a sacerdotal system, meaning salvation is mediated through the priesthood and the sacraments. Rome observes seven sacraments believed to operate ex opere operato, which means they automatically convey grace simply by the performance of the rite. Two of these sacraments represent a massive dividing line. Through penance, Rome teaches that penitent sinners must perform works of satisfaction to earn merit. Through the Eucharist, Rome teaches transubstantiation, the belief that the bread and wine are supernaturally transformed into the actual physical body and blood of Christ, and that the Mass is a sacrifice where Christ is offered again. Protestants insist that Christ's sacrifice on the cross was full, final, and sufficient.

4. The Church and Salvation.

Rome historically held to the formula extra ecclesiam nulla salus, meaning "outside the church, no salvation." While modern Catholicism has softened this language by calling Protestants "separated brethren," Rome still fundamentally views itself as the only true church and the mystical body of Christ. Protestants distinguish between the visible church and the invisible, universal church, which consists of all the elect gathered under Christ, their only Head.

5. The Papacy and Infallibility.

In 1870, Vatican I formally defined the dogma of papal infallibility. Rome requires all faithful Catholics to believe that when the pope speaks ex cathedra on matters of faith and morals, he speaks without error. Protestants completely reject this claim, declaring that the position of head of the church belongs exclusively to the Lord Jesus Christ.

6. Mariology.

Rome officially teaches the immaculate conception of Mary, her bodily assumption into heaven, and her ongoing role as Advocate and Mediatrix. Millions of Catholics pray to Mary to intercede for them. Protestants honor Mary as a supreme model of faith, but they insist on the biblical truth of solus Christus: Christ is the singular and completely sufficient Mediator between God and man.

Why Do Catholics Rely on Church Tradition and the Pope Instead of the Bible Alone?

A Roman Catholic would say that the Bible alone is not enough. Catholic teaching holds that God's revelation consists of two equal parts: Scripture and Tradition. Tradition, in this view, is the unwritten oral teaching of Jesus passed down through the bishops of the church. Both must be accepted with equal devotion and reverence. Within this framework, the Pope is viewed as the successor of Peter, granted supreme authority over the entire church, and protected by divine infallibility when he speaks officially on faith and morals.

An evangelical Christian answers differently. The Bible alone is the ultimate authority for doctrine and practice. Special revelation is found only in Scripture. Protestants affirm the sufficiency and clarity of the Bible. They believe it provides everything a person needs to be saved and everything a believer needs to please God, without the addition of church traditions. Regarding the Pope and church councils, Protestants point to the historical stance of the Reformers, who argued that popes and councils can and have erred and contradicted one another. The Westminster Confession of Faith summarizes the evangelical position clearly: the Supreme Judge of all religious controversies is not a pope or a church, but "the Holy Spirit speaking in the Scripture."

Do Catholics Believe They Have to Earn Their Salvation Through Works?

A Roman Catholic would say no, not through independent human effort, because the process begins with God's grace. However, the Catholic system teaches that salvation is a lifelong collaborative process in which the believer must cooperate with God's grace and perform good works to merit eternal life. Grace is infused into the soul at baptism, and this infused grace transforms the believer so they can perform deeds that genuinely merit heaven. If a Catholic commits a mortal sin, they must be restored through penance, which requires works of satisfaction to earn congruous merit.

An evangelical Christian would say that this system absolutely requires individuals to earn their salvation. While Protestants acknowledge that Rome teaches the necessity of grace and faith, they object to Rome's insistence on faith plus works, grace plus merit, Christ plus inherent righteousness. Protestants affirm sola fide: justification by faith alone. The only ground for salvation is the perfect righteousness of Jesus Christ, imputed to the believer the moment they exercise saving faith. Works and obedience are the necessary fruit and visible demonstration of a living faith, but they contribute nothing to the ground of a person's justification before God.

Why Do Catholics Pray to Mary and the Saints Instead of Going Directly to Jesus?

A Roman Catholic would say that praying to Mary and the Saints does not mean treating them as equal to Jesus. The Catholic Church draws a distinction between latria (worship due to God alone) and dulia (veneration given to Mary and the saints). Because Mary collaborated in Christ's redemptive work, Catholics believe she continues to bring believers the gifts of eternal salvation through her intercession. Catholics regularly invoke Mary under titles such as Advocate, Helper, and Mediatrix.

An evangelical Christian would say that believers should pray directly and only to God, because Jesus Christ is the one and only Mediator between God and man. Protestants believe that assigning Mary titles like Mediatrix and Co-Redemptrix seriously detracts from the finished work of Jesus on the cross. While Protestants highly respect Mary as a model of faith and obedience, they find no biblical evidence for her bodily assumption into heaven. And because Protestants believe that bowing before statues and praying to deceased human beings constitutes the essence of worship, they view these practices as crossing the line into idolatry.

Do Catholics Really Believe the Communion Wafer Becomes the Literal Body and Blood of Jesus?

A Roman Catholic would say yes, explaining this through the doctrine of transubstantiation. Catholic theology teaches that when the priest speaks the words of consecration, the inner substance of the bread and wine is supernaturally transformed into the literal body, blood, soul, and divinity of Jesus Christ, even though the outward appearance remains bread and wine. Because the host is believed to literally be Jesus, Catholics kneel, genuflect, and offer adoration to it.

An evangelical Christian would say no. Protestants believe that the bread and wine remain truly and only bread and wine. The Lord's Supper is an ordinance of remembrance. The bread and wine are powerful symbols meant to portray the gospel and prompt believers to remember Christ's saving death. Protestants raise several serious objections. First, Jesus ascended bodily into heaven and is no longer physically present on earth. Second, claiming Christ's physical body can exist on thousands of altars simultaneously wrongly assigns a divine attribute to His human nature. Third, Protestants reject any notion that the Mass is a sacrifice, insisting that Christ's atoning sacrifice was perfect, sufficient, and once for all.

Where Is Purgatory in the Bible, and Does It Undermine the Sufficiency of Christ's Cross?

A Roman Catholic would say that Purgatory does not undermine the cross but is a necessary part of how God prepares believers for heaven. Because Catholic theology teaches that God will only admit a person into heaven if righteousness truly exists within their soul, and because most believers fall short of that standard in this life, they must go to Purgatory. It is described as a place of loving, sanctifying chastisement where impurities are cleansed. Catholics defend this doctrine using their broader biblical canon (including the Apocrypha) and the equal authority of Church Tradition.

An evangelical Christian would say that Purgatory is entirely unbiblical and represents a severe denial of the sufficiency of Christ's cross. Protestants find no valid scriptural evidence for it and view it as a man-made invention. More importantly, Protestants reject the theology that makes Purgatory necessary. They believe that justification is based entirely on the alien righteousness of Christ imputed to the believer the moment they exercise saving faith. Because the believer is instantly declared perfectly righteous before God based on what Christ accomplished, Purgatory is completely unnecessary. No further purification after death is needed or possible.

Why Do Catholics Confess Their Sins to a Priest Instead of Directly to God?

A Roman Catholic would say that confessing to a priest is necessary because it is an essential part of the sacrament of penance. When a baptized person commits a mortal sin and loses saving grace, the sacrament provides a "second plank" of justification. The priest speaks in the name of Jesus Christ, exercising the authority to "bind and loose." But the sacrament does not end with confession. The priest must also prescribe works of satisfaction, such as specific prayers or almsgiving, to make amends and earn congruous merit so that God restores the sinner to a state of grace.

An evangelical Christian would say that believers should confess their sins directly to God, because Jesus Christ is the sole Mediator between God and humanity. While historical Protestants did not completely reject confessing struggles to a pastor for counsel, the core evangelical objection is directed at the requirement of works of satisfaction. Protestants reject the idea that after confessing, a believer must perform works to satisfy God's justice or earn merit to be restored to grace. This system adds human merit to the gospel and denies that Christ's once-for-all sacrifice was entirely sufficient to pay for all sins.

Can a Catholic Ever Know for Sure They Are Going to Heaven?

A Roman Catholic would say that a believer generally cannot claim absolute certainty. Because salvation is a lifelong collaborative process, and because justifying grace can be lost entirely through mortal sin, Catholics maintain a confident hope that they will persevere to the end. The Catholic view of justification is analytical: God will only declare a person just if He examines their life and finds them actually and inherently righteous. Because most believers fall short in this life, they must undergo Purgatory before entering heaven.

An evangelical Christian would say that a believer absolutely can know for sure. Protestants reject the idea that God only accepts a person based on their inherent righteousness. If getting into heaven required a person to arrive at a state of pure righteousness without any imperfections, every Christian would completely despair of ever being saved. Instead, the Protestant view rests on imputation. The perfect righteousness of Jesus Christ is credited to the believer's account the very moment they exercise saving faith. Because salvation is a completed legal declaration rather than a lifelong process of accruing merit, a Christian's assurance is rooted entirely in the promises of Christ and His fully sufficient, finished work.

Is the Pope Really Infallible?

A Roman Catholic would say yes, but with specific qualifications. Papal infallibility does not mean the Pope is perfect in his daily life. It means that when the Pope speaks ex cathedra to define a doctrine concerning faith or morals to be held by the whole church, he is protected from error through divine assistance promised to him as the successor of Peter.

An evangelical Christian would say no. Only one Man has ever spoken infallibly: Jesus Christ. And the Scriptures are the only infallible communication from God. The Reformers argued that popes and councils lack ultimate authority because they are fallible, can make mistakes, and have historically contradicted one another. The Westminster Confession of Faith explicitly states that Jesus Christ is the sole Head of the Church, and the Pope of Rome cannot in any sense claim that title. An evangelical relies entirely on the infallible Word of God rather than the decrees of any fallible human leader.

Why Do Catholic Bibles Have Extra Books (the Apocrypha)?

This question connects directly to the issue of authority. A Roman Catholic would say that the Church was granted an infallible ability to recognize and assemble the canon, making the Catholic Bible an infallible collection of infallible books. Rome includes the deuterocanonical writings because it believes its authority extends to determining which books belong in Scripture.

Protestants reject the Apocrypha as uninspired. They believe the church is fallible, and therefore the canon is a fallible collection of infallible books, guided by the inward witness of the Holy Spirit. The books themselves carry divine authority because God is their author, not because any church council declared them authoritative. The difference is significant: for Rome, the church stands over Scripture to authenticate it. For Protestants, Scripture stands over the church to judge it.

5 Helpful Tips for Christians Engaging with Roman Catholics

Understanding the theological differences is essential. But knowledge without love accomplishes nothing. If you have Roman Catholic family members, friends, or neighbors, here are five practical ways to engage with them faithfully and lovingly.

1. Build a genuine, loving relationship and never treat them as a project.

The foundation of sharing the gospel with Roman Catholic loved ones is a strong, loving relationship. If you have left the Catholic Church yourself, guard against bitterness or resentment. Venting anger will destroy the relationship and close the door to the gospel. Express your love by praying for their specific needs and offering practical help. Befriend them. Spend genuine time with them. Earn the right to lovingly discuss your differences. And even if they push back or grow frustrated with you, never stop loving them.

2. Start a reading group based on their liturgical calendar.

One of the most effective and non-confrontational approaches is to invite a Catholic friend to read the Bible with you. Base your study on the Gospel text scheduled for their upcoming Sunday Mass. If they attend Mass that week, they will have already been immersed in the same passage. Keep the format simple: read the text twice, pray for understanding, and walk through three steps of observation, interpretation, and application. The goal is to focus entirely on who Jesus is and what He does. Many Catholics are largely unfamiliar with the biblical Christ, and simply reading the Gospels together can be transformative.

3. Gently demonstrate the authority and clarity of Scripture.

As you read the Bible together, you will likely encounter two common responses rooted in Catholic teaching. If your friend says, "My priest said X about this text, but you said Y," do not argue about authority. Gently guide them back to the passage by asking, "But you have read the text. What does the Bible say?" This subtly establishes the authority of Scripture over church hierarchy. If they express caution about reading the Bible because they have been told it is too difficult for laypeople, respond by pointing to your shared experience: "But we read the Bible together, and we do not find it too difficult, do we?" This practical exercise naturally promotes the clarity of Scripture without requiring a theological debate.

4. Take your time and carefully clarify the difference between "faith alone" and "faith plus works."

Do not rush the process. It may take months for a Catholic to understand who Jesus truly is and what He has done. Do not push anyone toward a commitment before they understand the gospel. When the time is right, you must carefully clarify the true gospel, because the Roman Catholic system uses the same theological vocabulary with entirely different meanings. Explain that while Catholicism teaches grace is infused to transform a person so they can merit eternal life, the Bible teaches that Christ's perfect righteousness is imputed to the believer by faith alone. Make it clear that the formula of "faith plus anything" cancels out true faith and renders salvation void.

5. Ask a revealing question to gauge their understanding.

Because Roman Catholics are taught that salvation is a lifelong process requiring their own meritorious good works, it can be difficult to know whether they have truly grasped the gospel of grace. Before encouraging them to turn to Christ, ask this question: "Have you ceased to rely on all your own efforts to earn God's love and forgiveness?" Listen carefully. If they answer by saying they are trying to attend Mass more regularly or working hard to be a better person, they are still relying on their own righteousness. But if they acknowledge that nothing they do can make God love them, they understand that salvation is received by faith alone. And you can take the next step of encouraging them to place their complete trust in Christ.

The differences between Christianity and Roman Catholicism are real and they are serious. But the people on the other side of those differences are made in God's image, and many of them are people we love deeply. We must understand the truth clearly enough to explain it. And we must love the people in front of us enough to explain it with patience, gentleness, and prayer.

Bibliography

• Allison, Gregg R. 40 Questions About Roman Catholicism. Grand Rapids, MI: Kregel Academic, 2021.
• Sproul, R. C. Are We Together? A Protestant Analyzes Roman Catholicism. Sanford, FL: Reformation Trust Publishing, 2012.