The fact that Celtic Christianity is different to Roman Catholicism in several ways, is largely due to the language barrier and the remoteness of the area. One of the most known differences with the Roman Catholicism is the determination of the date of Easter. There are several ways to do this, and those ways have changed and refined through the centuries. After the establishment of the Celtic Church, there was a time where there was relatively little contact with the rest of Europe and when that contact was renewed, it appeared that the Roman Catholic Church had adopted a different system. Several Celtic parishes practiced this system, while others maintained the old system. There is a striking difference in the conception of the original sin. The Catholic saint Augustine argued that the original sin was caused by Adam and Eve eating the forbidden fruit in Paradise, and that this sin was transmitted to their offspring and therefore all people. To get rid of the original sin, people had to live by the Bible and fulfil God's will. The Celtic monk Pelagius, however, claimed that this original sin did not exist and that a good and sinless life would be enough to go to heaven.