Roman Catholicism shares the central doctrines of historic Christianity with other major Christian traditions. Catholics believe in one God—Father, Son, and Holy Spirit—and affirm that Jesus Christ is truly God and truly human, that He died and rose bodily from the dead, and that salvation is possible only because of God’s grace through Christ.

The major disagreements between Roman Catholicism and Protestant Christianity generally arise elsewhere. They concern questions such as how divine revelation is transmitted, who has authority to interpret it, how justification should be understood, how grace is received, and what happens to believers after death. Those disagreements became particularly important during the Protestant Reformation, but many of them have roots extending much farther back in Christian history.

Scripture and Sacred Tradition

Catholics accept the Bible as the inspired Word of God, but Catholicism does not teach sola Scriptura, the Protestant principle that Scripture is the church’s final and uniquely infallible authority. Instead, Catholic teaching speaks of Sacred Scripture and Sacred Tradition as closely connected means by which the apostolic faith has been handed down to the church.

Sacred Tradition does not simply mean customs that developed over time. In Catholic theology, it refers to the apostolic teaching entrusted to the church and transmitted through its life and teaching. Scripture and Tradition therefore belong to what Catholics understand as a single deposit of faith rather than two competing sources of revelation.

The authoritative interpretation of this deposit belongs to the church’s Magisterium, or teaching office, exercised by the bishops in communion with the pope. This creates one of the fundamental differences between Catholic and Protestant approaches to Christian doctrine: the disagreement concerns not merely the interpretation of particular Bible passages, but who possesses the authority to settle questions of interpretation in the first place.

Grace and Salvation

Catholicism teaches that salvation begins with God’s grace. Human beings cannot earn salvation through their own natural abilities or perform enough good works to place God in their debt. God’s grace precedes and enables the human response to Him.

At the same time, Catholic theology does not generally describe salvation as a single past event. Salvation involves forgiveness, justification, sanctification, perseverance, and ultimately eternal life. Grace is received and lived out within a relationship with Christ that includes faith, the sacraments, obedience, and participation in the life of the church.

This is an area where Protestant descriptions of Catholicism can sometimes become caricatures. Saying simply that “Protestants believe in grace while Catholics believe in works” does not accurately represent Catholic teaching. The real disagreement is more complicated and concerns the relationship between grace, faith, justification, transformation, and human cooperation with grace.

Justification

The doctrine of justification became one of the defining controversies of the Protestant Reformation. Martin Luther and other Reformers argued that sinners are justified by faith apart from works and that Christ’s righteousness is credited to the believer. This became associated with the Reformation principle of sola fide—“faith alone.”

Catholic theology also teaches that justification is made possible entirely through Christ and God’s grace, but it understands justification as involving an actual transformation of the person rather than only a declaration concerning the believer’s standing before God. The grace that forgives also begins to make the sinner righteous.

The Council of Trent, meeting during the sixteenth century in response to the Reformation, formally articulated the Catholic position and rejected important elements of the Protestant understanding of justification. Catholics and Protestants have continued discussing the subject ever since, and later ecumenical dialogue has identified areas of agreement that sometimes get lost in popular arguments. Nevertheless, significant differences remain.

Merit and Good Works

Catholic references to merit can sound especially strange to Protestant ears because the word can suggest earning salvation independently of grace. That is not how Catholic theology understands it. Catholic teaching maintains that even the believer’s ability to perform genuinely good works depends upon God’s prior grace.

Catholicism nevertheless teaches that believers can cooperate with grace and that acts performed in grace have genuine significance before God. This understanding fits within a larger Catholic view of salvation as something God accomplishes in people rather than merely a change in their legal status.

The disagreement with Protestant theology therefore isn’t adequately summarized by asking whether Christians should do good works. Virtually everyone agrees that they should. The more important question is what relationship those works have to justification and final salvation.

Purgatory

Catholicism teaches that some people who die in God’s grace may still require purification before entering the fullness of heaven. This state or process of final purification is called purgatory. It is not understood as a second opportunity for the unsaved to become Christians, nor is it identical to hell. Those undergoing purification are understood to be destined for heaven.

Catholics have appealed to biblical passages as well as the practice and tradition of the church in support of the doctrine. Protestants generally reject purgatory, arguing that Scripture does not establish such an intermediate purification and that Christ’s saving work is sufficient for the believer’s acceptance before God.

Because purgatory touches questions about justification, sanctification, judgment, prayer for the dead, and the authority of church tradition, the disagreement cannot really be understood in isolation from the larger Catholic theological system.

Mortal and Venial Sin

Catholic theology distinguishes between mortal and venial sin. Venial sin damages a person’s relationship with God but does not destroy the life of grace within the soul. Mortal sin involves grave matter committed with sufficient knowledge and deliberate consent and results in the loss of sanctifying grace.

A Catholic who commits mortal sin is ordinarily reconciled to God through repentance and the sacrament of Penance, commonly called Confession. This distinction has important implications for Catholic teaching about salvation, the sacraments, and Christian moral life.

Many Protestants reject this particular classification of sins, although Protestant traditions also recognize differences in the seriousness and consequences of sinful actions. As with many Catholic doctrines, understanding the terminology is important before deciding whether the underlying theology is biblical.

A Connected System

Catholic doctrines make the most sense when they are understood together. Scripture and Tradition relate to the authority of the Magisterium. The Catholic understanding of grace relates to justification and good works. Those teachings connect with the sacraments, Confession, mortal sin, and purgatory. Pulling one doctrine out of that system can easily produce a distorted picture of what Catholics actually believe.

That does not mean the system is necessarily correct. It means that evaluating it fairly requires understanding what it claims before deciding whether those claims agree with Scripture.

For Jew & Greek, that distinction will be important. Our deeper articles can examine sola Scriptura, justification, purgatory, merit, mortal sin, and other disputed doctrines individually. This introductory page gives us the framework in which those discussions belong.