The Plymouth Brethren are a conservative, low church, nonconformist, Evangelical Christian movement whose history can be traced to Dublin, Ireland in the late 1820s, originating from Anglicanism. Among other beliefs, the group emphasizes sola scriptura, the belief that the Bible is the supreme authority for church doctrine and practice over and above "the [mere] tradition of men" (Mark 7:8). Brethren generally see themselves, not as a denomination, but as a network (or even as a collection of overlapping networks) of like-minded independent churches. (The Brethren would generally prefer that their gatherings be referred to as "assemblies," rather than "churches" but, in the interests of simplicity, this article uses both terms interchangeably.)
An influential figure among the early Plymouth Brethren was John Nelson Darby (1800 – 1882). The movement refused to take any denominational name to itself, a stance that some still maintain. The title "The Brethren," however, is one that many of their number are comfortable with, in that the Bible designates all believers as "brethren"—"one is your Master, even Christ; and all ye are brethren" (Matthew 23:8).
"Brethren assemblies" (as their gatherings are most often called) are divided into two major branches: the "Open Brethren" and the "Exclusive Brethren", following a schism that took place in 1848. The general category "Exclusive Brethren" has been confused in the media with a much smaller newsworthy group, numbering only around 40,000 worldwide, known as the Plymouth Brethren Christian Church (PBCC) or the Raven-Taylor-Hales Brethren. Both of these main branches are themselves divided into several smaller streams, with varying degrees of communication and overlap among them.
The best-known and oldest distinction between Open and Exclusive assemblies is in the nature of relationships among their local churches. Open Brethren assemblies function as networks of like-minded independent local churches. Exclusive Brethren are generally "connexional" and so feel under obligation to recognise and adhere to the disciplinary actions of other associated assemblies. Disciplinary action normally involves denying the individual participation in the "breaking of bread" or "Lord's Table." (Generally, this is a weekly, Sunday morning, hour-long service of prayer, singing, teaching, and taking of communion, with important assembly-related announcements given at the end. Exclusion from it is a major issue.) Discipline may also involve formal social ostracism or "shunning" to varying degrees, dependent upon which kind of Brethren group it is. (For instance, people placed "under discipline" may be asked not to attend any group functions which are purely social, and people may decline to eat with, or even shake hands with, members who are under discipline.)