On October 31, 1517 Martin Luther nailed his 95 Theses on the door of the church in Wittenberg. That moment is recognized as the start of the Protestant Reformation. Today most of the major Christian denominations trace their beginnings to those early years of the Reformation.

The largest Christian church in the world did not begin in the 1500’s but hundreds of years earlier. The Roman Catholic church has over 1 billion professing adherents. Until the Reformation Catholicism was the supremely dominant expression of Christianity throughout Europe. If the Reformation was a response to the Catholicism of the Middle Ages when did Catholicism begin?

The official teaching of the Catholic church is that it started when Jesus told Peter, “That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.” (Matthew 16:18) Most historians view the beginning of the Catholic church as much later than this. However, establishing a firm starting point for the Catholic church is nearly impossible.

Some trace the beginning of the Catholic church to the planting of the first church in Rome. Some believe the Catholic church started during the reign of Constantine. Emperor Constantine declared himself a convert to Christianity in 311 AD. He made Christianity legal in the Roman Empire and is said to have been the first Christian emperor. Others date the beginning of Catholicism with the rise of Pope Leo I in the mid-400’s.

Identifying the beginning of Catholicism is not easy. Catholicism did not step onto the world stage as a fully developed religion. What we know today as Catholicism rose slowly over many years. For example, the uniquely Catholic doctrine of the papacy took many decades to develop. The authority of the Bishop of Rome can be seen to increase during the leadership of several Bishops of Rome. The rise of Pope Leo I saw the culmination of this development. He was not the first to teach a single man was head over the worldwide church but he was the first to successfully implement near universal leadership.

Other distinctive doctrines, like the veneration of Mary, also arose gradually. The first statement that points towards the elevation of Mary in official teachings comes from the council of Ephesus in 431 AD. During that council she was established as the “God-bearer”. Prayer to Mary possibly existed much earlier, but by 600 it was a routine practice. Not until 1854 did a Catholic Pope establish Mary’s immaculate conception as official church teaching.

Similarly, prayer to the saints was being practiced as early as a couple hundred years after the death of Christ. The increase of this practice can be traced throughout the Dark Ages but it was not until 1545 that the Catholic church officially stated its doctrine regarding praying to saints.

Catholicism as it stands today is the result of centuries of growth and change. Its origin was gradual. The Roman Catholic Church grew out of a series of political situations, ecclesiastical decisions, popular beliefs and influential doctrines that merged together to become Roman Catholicism. Though a specific beginning cannot be identified by the late 400’s the Catholic church was in place and increasing in power.