Here's why...

In Matt 16: 17-19

Jesus changes Simon's name (means little grain of sand in Aramaic) to Kepha (means massive rock in Aramaic; Peter) and says "upon Kepha I will build my Church and the gates of hell will never overpower it." - though hell is trying very hard to overpower it in today's world! Jesus then gives Peter (1st Pope) the keys to the kingdom of heaven and says, "whatever you bind on earth will be bound in heaven; whatever you loose on earth will be loosed in heaven."

The Church has binding and loosing authority. Think about that for a minute. If it is bound in heaven it has to be perfect because heaven is perfect. This is the basis for authority and infallibility of the Church.

Now... to how all christians FOLLOW the authority and infallibility of the Catholic Church:

The Catholic Church compiled the New Testament of the Bible in 382AD during the Council of Rome (see link below). The Church leaders under Pope Damasus I used the binding and loosing authority and infallibility of the Catholic Church to vote on what books and letters should be in the Bible or not. They voted out the gospel of Hebrews for example but voted in Matthew, Mark, Luke and John. There were thousand of books and letters that the Church had to review which many authors thought were inspired by the Holy Spirit.

If you don't believe in the authority and infallibility of the Catholic Church that compiled the New Testament then you will have to claim the New Testament is invalid and wrong.

[link to en.wikipedia.org (secure)]

God Bless! Jim