Quakers (or Friends) are members of a historically Christian group of religious movements generally known as the Religious Society of Friends. Members of the various Quaker movements are all generally united in a belief in the ability of each human being to experientially access "that of God in every person," and therefore they profess the priesthood of all believers, a doctrine derived from the First Epistle of Peter. They include those with evangelical, holiness, liberal, and traditional Quaker understandings of Christianity. To differing extents, the different movements that make up the Religious Society of Friends/Friends Church avoid creeds and hierarchical structures. In 2007, there were approximately 359,000 adult Quakers. In 2012, there were 377,055 adult Quakers.