Roman Catholicism
Most Catholics believe in the Trinity, that Jesus is God, and that he died and rose again. The difference is how a person is forgiven and made right with God. Each point below comes from official teaching still in force today, mostly the Catechism and the Council of Trent, and links to the original so you can read it yourself.
We are not saved by faith alone
The Council of Trent declared anyone who teaches that we are made right with God by faith alone to be "anathema" (condemned). Rome teaches that God pours grace into us so we actually become good, and we must cooperate with it.
We are made right with God by trusting Christ alone. His perfect righteousness is credited to us as a free gift, not earned by us.
Romans 3:28; Romans 4:5; Galatians 2:16; Philippians 3:9
Official source: Council of Trent, Session VI, Canons 9 & 11
Good works can merit eternal life
The Catechism teaches that after the first grace, "we can merit for ourselves and for others all the graces needed to attain eternal life". This grace can be lost through mortal sin and restored through confession.
Eternal life is a gift we receive, never wages we earn. Those who belong to Christ are kept by him and cannot be snatched away.
Romans 6:23; Ephesians 2:8-9; Romans 11:6; John 10:28-29
Official sources: Catechism 2006–2011, Catechism 2027
Church Tradition is equal to the Bible
The Catechism says the Church "does not derive her certainty about all revealed truths from the holy Scriptures alone", and that only the Church's teaching office can interpret them.
Scripture is God's own word and the final authority that judges all church teaching and tradition, not the other way around.
2 Timothy 3:16-17; Mark 7:8-13; Acts 17:11; Isaiah 8:20
Official sources: Catechism 80–82, Catechism 85–87
The Pope can teach without error
When the Pope formally defines a teaching on faith or morals, the Catechism says he "enjoys this infallibility in virtue of his office", and the faithful must accept it.
Christ alone is head of the church. Even the apostle Peter was publicly corrected when he went against the gospel.
Ephesians 1:22-23; Colossians 1:18; Galatians 2:11-14; Matthew 15:9
Official sources: Catechism 891, Catechism 2035
The Mass is a sacrifice that takes away sins
The Catechism calls the cross and the Mass "one single sacrifice". The same Christ is offered again at every Mass through the priest, for the sins of the living and the dead.
Christ offered himself once for all, and his sacrifice is finished. It is never repeated, and no further offering for sin is needed.
Hebrews 7:27; Hebrews 9:25-28; Hebrews 10:10-18; John 19:30
Official source: Catechism 1366–1367
The communion bread is to be worshipped as Jesus
Rome teaches the bread and wine become Christ's actual body and blood (transubstantiation), so the bread is given "the cult of adoration", both during Mass and when displayed outside of it.
Jesus gave the bread and cup as a remembrance of his death. Worship belongs to God alone, and the bread remains bread.
Luke 22:19-20; 1 Corinthians 11:24-26; Exodus 20:4-5; Matthew 4:10
Official sources: Catechism 1376–1378, Catechism 1418
Punishment for sin remains and can be reduced by indulgences
Even after forgiveness, Rome teaches "temporal punishment" remains, paid in this life or in purgatory. Indulgences reduce it by drawing on a "treasury" of the merits of Christ, Mary and the saints.
Christ's death fully paid for the sins of those who trust him. There is no condemnation left and no debt for us or the saints to pay.
Romans 8:1; Hebrews 10:14; 1 John 1:7; Colossians 2:13-14
Official source: Catechism 1471–1479
Mary was sinless and was taken bodily into heaven
Catholics must believe Mary was conceived without sin and was "taken up body and soul into heavenly glory". These were declared by popes in 1854 and 1950, not taught from the Bible.
All have sinned except Christ, and Mary herself called God her Saviour. We are only bound to believe what Scripture teaches.
Luke 1:46-47; Romans 3:23; Hebrews 4:15; 1 Corinthians 4:6
Official sources: Catechism 491, Catechism 966, Ineffabilis Deus (1854), Munificentissimus Deus (1950)
Mary is a mediator, and we should pray to the saints
The Catechism calls Mary "Advocate, Helper, Benefactress, and Mediatrix", and teaches that we should ask the saints in heaven to pray for us.
There is one mediator between God and people, Jesus Christ. We can come boldly to God through him, and prayer belongs to God alone.
1 Timothy 2:5; Hebrews 4:14-16; John 14:13-14; Matthew 6:9
Official sources: Catechism 956, Catechism 969, Catechism 2677
Statues, images and relics should be venerated
The Catechism teaches that images of Christ, Mary and the saints are owed "respectful veneration", and that relics of saints are honoured. Catholics bow before, kneel at and kiss them.
God commands us not to bow down to images. Calling it honour rather than worship does not change what the command forbids.
Exodus 20:4-5; Isaiah 42:8; Acts 10:25-26; 1 John 5:21
Official sources: Catechism 2129–2132, Catechism 1674
The true Church is the one under the Pope
The Catechism teaches that the Church of Christ "subsists in" the Catholic Church, "governed by the successor of Peter", and that the fullness of the means of salvation is found only there.
The true church is all who trust in Christ, wherever the gospel is rightly preached. Christ, not Peter, is the foundation.
1 Corinthians 3:11; Ephesians 2:19-22; Galatians 3:26-29; 1 Peter 2:4-6
Official source: Catechism 816, 846
The Apocrypha is Scripture
In 1546 the Council of Trent added Tobit, Judith, Wisdom, Sirach, Baruch, 1–2 Maccabees and extra parts of Daniel and Esther to the Old Testament, and declared anyone who rejects them "anathema".
The Old Testament is the one God entrusted to the Jews, which Jesus and the apostles quoted. These extra books can be useful history but are not God's word.
Romans 3:1-2; Luke 24:44; Matthew 23:35
Official source: Council of Trent, Session IV