It is common to think that Christians and Catholics believe the same things except with a few nuances. For example, it is a common knowledge that Catholics worship both Jesus and Mary, mother of Jesus, and Christians worship only Jesus Christ. However, in reality, the differences are even more significant than we think from a theological perspective, and it is essential to know what they are. Who knows this can be a perfect Segway to share the gospel of Jesus Christ. Let's get right to it.
1. Pope is the head of the Church
It is in the Roman Catholic teaching that Jesus made Simon, whom he named Peter the "rock" of this Church. They also believe that Jesus gave him the keys of his Church and appointed him as the shepherd of the entire Church. The bishops continue the pastoral office of Peter and other apostles under the authority of the pope.
It seems they have come to that conclusion from Matthew 16:18-19. When I first read that passage, I have to admit that I agreed with them for a moment. It is common for anyone to come to that conclusion on your first read. The question is whether those teachings are in agreement with scripture.
Consider Acts 15:1-23, Galatians 2:1–14 we see all other apostles are equally involved and authoritative in the ministry of the gospel. In1 Peter 5:1–5, he wrote, "So I exhort the elders among you, as a fellow elder." He considers himself as a fellow elder, not as a primal voice of the Church.
While Peter was central in the early spread of the gospel, the teaching of scripture, taken in context, nowhere tells us that he was in authority over the other apostles or the Church nor is it ever taught that bishop of Rome was to have supremacy over the Church.
2. Catholics worship Mary
Catholics believe that worship and adoration are due to God alone. Catholics do, however, worship Mary. In other words, they honor Mary with great reverence and devotion because she is the Mother of God.
Mother Theresa once prayed to Mary, asking to give a heart so beautiful and pure that I may receive Jesus in the Bread of Life. What does scripture say about this kind of prayer? Never in the scripture mentions or encourages this kind of prayer. They replace the priestly ministry of Jesus Christ with Mary. There is nothing wrong in desiring the heart and humility of Mary, but praying to her is an offense to God.
In 1 Tim 2:5: "For there is one God, and there is one mediator between God and men, the man Christ Jesus…". Praying to the saints goes against the scripture because we are making them mediators between God and man, diminishing Jesus' role as the sole mediator.
There is one theme running through the text in the letter to the Hebrews, and it's his superiority especially the perfect effectiveness of his sacrifice for sin and his immediate intercession at the right hand of the father for the people given to Him by the His Father. Isn't that in Jesus Name we come to the father in our day to day prayers? If the worship is due to God alone, then it is expected to God alone.