Old Believers

The Old Believers (Russian: староверы) are a sect of Eastern Orthodox Christians that separated from the Russian Orthodox Church in 1666. They are notable for rejecting the reforms of later Eastern Orthodoxy.

Origins
In 1652 Patriarch Nikon of Moscow noticed slight differences between the rituals and liturgy of the Russian and Greek Orthodox Churches. Unable to tolerate even the slightest difference of opinion or practice, Nikon naturally changed the Russian rite to exactly match the Greek rite, and banned all Russian practices different from the Greek ones. (Ironically, the Russian practices were often the original ones.)

Consequences
The changes made were, overall, incredibly minor, along the scale of a few letters, or repeating a few words. One conspicuous change was in the number of fingers used when making the Sign of the Cross. The Old Believers made the sign with two fingers and curled the thumb together with the ring and pinky fingers, while the reformers used three—the thumb and first two fingers—and curled the remaining two fingers to the side; in both cases the two fingers represent the dual nature of Jesus as both Man and God, while the three represent the Holy Trinity. However, there was a massive protest to these changes, the punishment for failure to go along with them was death, and surviving Old Believers were persecuted for centuries afterward. Thus, the New Atheist claim that "Religious people have been known to kill each other over the number of fingers used in a ritual blessing" is not, in fact, a fabrication—though it is citing an extreme example.