The Baptist view of ecclesiology (the doctrine of the Church) constitutes one of the core distinguishing features of the tradition, and is fundamental to both its theology and its practices. This view is grounded in and focuses on local congregations of Christians, rather than some larger, collective organization or institution. It can be readily understood through the consideration of the Baptist view of the nature of the Church, the order of the Church, and the purposes of the Church.
First, according to the Baptist tradition, the Church consists of and in people. It is neither a building nor an organization. This belief is based in part on the root of the Greek New Testament term often translated "church," the term ekklesia. In general Greek usage, this term referred to an "assembly" or group of people.
Furthermore, the people thus identified are neither people in general nor "everyone"; rather, a particular subset or group of people is in view. The term ekklesia is derived from two Greek elements: the prefix ek- ("out of" or "out from") and the verb kaleo ("to call" or "to summon"). Thus, these people are "called-out ones." They are, as a group, a distinct community of people, and what makes them distinct is that they are called-out by God. According to Baptist belief, the ekklesia, the Church, this community of people, is what it is not by virtue of something that its people have done but by virtue of something that God has done; namely, God has called these people, saved them, and set them apart.
In the process of calling them and setting them apart, God gives new spiritual life, sometimes referred to by Baptists as being "born again" or "regenerate." This community, the church, thus consists entirely of people who are regenerate. It is particularly at this point that the matter of baptism is so important to Baptists. The church community is not a "mixed" reality, consisting of both regenerate and unregenerate people, but rather of regenerate people only. So, how is it known whether a person is regenerate and thus properly admitted into a church community? After a person's beliefs and life are examined and affirmed by the leaders of a church, that person is accepted for baptism and that person testifies to God's saving work in his or her life through the act of baptism.
Implicit in this is the fact that only persons old enough to make a conscious, intentional decision to entrust themselves to Jesus Christ, and a subsequent decision to be baptized, are in view here. The importance of this is manifest in the fact that in the Baptist tradition (as well as Anabaptist traditions), the people who constitute the church community are often referred to as "believers," and baptism is often referred to as "believer's baptism" or "adult believer's baptism."
Second, the Baptist view of the order (or polity or government) of the Church serves to highlight a number of important and characteristic Baptist beliefs. Each local congregation is autonomous. This autonomy has two dimensions: one ecclesiastical, the other civil. Each local church is independent, and there is no higher ecclesiastical authority or body, such as a synod or a denomination, to which it is subject. Baptist churches may be related to one another through voluntary participation in an "association" or "convention" or "fellowship," but they avoid the use of either the term "church" (because of their interpretation of New Testament passages that describe churches) or the term "denomination" (because this usually denotes a measure of external control over local churches) to refer to these larger, collective organizations. Baptists clearly stress the voluntary nature of participation in such an association.
The second dimension of the Baptist notion of local church autonomy is embodied in the separation of Church and state, properly understood. While in no way commending a religionless or churchless civil society--in fact, quite the contrary is the case--the Baptist tradition has always been, and continues to be, an advocate of the separation of church and state. Local churches are not to be authoritatively overseen, particularly with respect to explicitly religious matters, by any level of civil government. Christ, and Christ alone, is ultimately the head of each local church, and he exercises direct headship over each church, "the body of Christ" (Romans 12:3-5; Ephesians 4:11-13). Baptists believe that the good of both the churches and society at large is served by governments' recognizing and not interfering with churches' God-given freedom, for in such a context churches will thrive and, thereby, both the people of the society and the society itself whole will be well served.