Why does Christianity have so many denominations?

Followers of Jesus span the globe. But the global body of more than 2 billion Christians is separated into thousands of denominations. Pentecostal, Presbyterian, Lutheran, Baptist, Apostolic, Methodist — the list goes on. Estimations show there are more than 200 Christian denominations in the U.S. and a staggering 45,000 globally, according to the Center for the Study of Global Christianity. So why does Christianity have so many branches? 

A cursory look shows that differences in belief, power grabs and corruption all had a part to play. 

But on some level, differentiation and variety have been markers of Christianity since the very beginning, according to Diarmaid MacCulloch, professor emeritus of church history at the University of Oxford in the United Kingdom. "There's never been a united Christianity," he told Live Science. 

Related: Was Jesus a magician?

Early splits

The early church, which spans from the start of Jesus' ministry, in A.D. 27, to A.D. 325, was divided primarily based on geography. Worship styles and interpretations of Jesus' teachings varied based on regional cultures and customs, according to Bruce Gordon, a professor of ecclesiastical history at Yale Divinity School.

But there were also major breaks, or schisms, over Christian theology during this time. One of the most notable early schisms, the Arian controversy in the early fourth century, divided the church on Jesus' relationship with God. Arius, a priest from Alexandria, Egypt, claimed that because Jesus was "begotten," or brought about by God, he was a lesser divinity than God. But Athanasius, an Alexandrian theologian, claimed that Jesus was God incarnate. 

"This caused major upheaval in the Roman Empire," said Christopher West, a doctoral student of ancient Christianity and medieval studies at Yale University. "It split Christians in the Roman Empire in half." The Council of Nicea — a group of theologians and scholars gathered by Emperor Constantine I in A.D. 325 — ultimately sided against Arius. But despite the church's official view, Christians continued to be divided on the subject for more than a century. 

Then, in 1054, the Eastern Orthodox Christians split from the Western Roman Catholics in what's known as the Great Schism. The two groups disagreed on the taking of the sacraments — religious symbols believed to transmit divine grace to the believer. Furthermore, the Eastern Orthodox Christians disagreed with the Roman beliefs that priests should remain celibate and that the Roman pope had authority over the head of the Eastern church, according to Encyclopedia Britannica.

There was even a temporary schism, known as the Western Schism, within the Catholic Church itself in 1378, when two men, and eventually a third, claimed to be the true papal heir. The division lasted almost 40 years, and by the time it was resolved in 1417, the rivaling popes had significantly damaged the reputation of the papal office. 

Despite this handful of schisms, the Catholic Church successfully suppressed other potential Christian offshoots "partly by sustained persecution [including] actual military expeditions against some labelled heretics, but then also a new system of enquiries into people's beliefs, called inquisitions. With the backing of secular rulers, heretics might be burned at the stake or forced into denying their beliefs," MacCulloch told Live Science via email.

Related: What led to the emergence of monotheism?

Denominations explode

But after the Protestant Reformation in 1517, the number of denominations really began to multiply. 

The Reformation — instigated by a number of events, most notably Martin Luther's 95 Theses — emphasized a personal faith. This movement was in reaction to the fact that interpretations of the Bible, grace (spontaneously given love and mercy from God), the absolution of sins and entry into heaven were all mediated through priests in Catholicism. Luther and his followers claimed that the Bible, not a church hierarchy, was the ultimate authority over all people, including priests and the pope, and that several ecclesiastical practices, such as granting indulgences (paying the church money to be absolved of sins), were corrupt.

Initially, there were just a few major Protestant groups, but ultimately, the Reformation ushered in more Christian offshoots.

By the 17th century, the contemporary word "denomination" began to be used to describe religious offshoots, Michelle Sanchez, an associate professor of theology at Harvard Divinity School, told Live Science via email. Protestants had used scripture to critique the Roman Catholic Church, claiming that any believer could read scripture and have a personal relationship with God. But then, "the obvious problem emerged: Whose interpretation of scripture was the right one?" Sanchez said in an interview. As believers debated the scriptures and sacraments, churches formed and split based on myriad biblical interpretations, ways of worship and organizational structures. From these debates, denominations such as the Presbyterians, Mennonites, Baptists and Quakers, among others, took root. 

Other Protestant denominations were formed out of a play for power, such as when Henry VIII started the Church of England in 1534. "He wanted to establish the political autonomy of England, and one way to do that was religious autonomy from Rome," West told Live Science. (He also famously wanted a divorce that the church refused to grant.)

Although schisms may be seen as divisive or even lead to violent conflicts between rival denominations, these splits do have an upside. "There's kind of an anti-corruption mechanism in the fragmentation," as these splits can offer agency to people in lower social positions, Sanchez said. For instance, after the Reformation challenged papal authority, townspeople could begin to question religious authorities about corrupt or questionable practices. 

There's likely more denominational splitting and forming to come. On judging the differences between them, MacCulloch offered advice from Jesus himself: "Ye shall know them by their fruits" (Matthew 7:16). That is, you can learn about them "in terms of what they do, their behavior," MacCulloch explained. "That's a pretty good test."

Originally published on Live Science.