God purposed (Ephesians 3:10,11) and Christ promised to build a church (Matthew 16:18). This church began after Jesus died, after the gospel was preached on the Pentecost after His death and when some who heard the gospel were baptized in the name of Jesus for the remission of sins (Acts 2:37,38,47). God adds those who are saved to His church (Acts 2:47); the church is the redeemed of the Lord.
God purposed only one church and Christ built only one church; all of the saved are a part of the one church. This church is sometimes referred to in scripture as "the body of Christ" (Ephesians 1:21,22). We are plainly told, "There is one body" (Ephesians 4:4). If we believe the Bible, we must admit that there is one church.
Many think that the one church is denominational. The word denomination means "a name or designation, especially one for a class of things" (Webster's Encyclopedic Unabridged Dictionary.) In religion, denominations are organized groups of congregations that can be denominated (named) or classified together because they have formed a collective entity. Denominationalism is made up of religious groups such as Methodists, Baptists, Presbyterians, Lutherans, Episcopalians, etc. - religious sects seeking to distinguish themselves from one another by different names because they have different doctrines, practices, and organizations. People espouse denominationalism when they join one of these religious groups, suggest that "one church is as good as another," or encourage people to "join the church of your choice."
Some think that Jesus sanctioned denominations when He said, "I am the vine, you are the branches" (John 15:5). They contend that "the branches" are different denominations. However, a careful reading of this verse and the verse that follows precludes such an interpretation. Jesus said, "I am the vine, you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing. If anyone does not abide in Me, he is cast out as a branch and is withered; and they gather them and throw them into the fire, and they are burned" (John 15:5,6). The pronouns, "he," "him," "anyone," and "he," show that the branches are individual disciples, not denominations. Furthermore, it is unfruitful disciples whom they gather and throw into the fire, and who are burned." In this scripture, Jesus did not endorse denominations!
The Bible does speak of "churches:" "the churches had rest" (Acts 9:31); "the churches of Christ salute you" (Rm. 16:16); "the seven churches which are in Asia" (Rev.1:4). However, the word "churches" in the New Testament never refers to denominations. The word church sometimes refers to the saved in a given locality, such as the "church at Jerusalem" (Acts 8:1) or "the church of God at Corinth" or "the church of Ephesus" (Rev. 2:1). In the New Testament, "churches" refers to the saved in a plurality of locations. For example, we read, "then had the churches rest throughout all Judea and Galilee and Samaria" (Acts 9:31). The same doctrine was taught in all of these churches (1 Cor. 4:17; 7:17; 16:1). Members of these churches all obeyed the same gospel to be saved (Gal. 1:6). These "churches" were not denominations. Denominationalism is not taught or approved by the Bible.
There is much that is wrong with denominationalism. Jesus prayed for unity among His believers (Jn. 17:20,21), and Paul condemned division saying that we should all be joined together in the same mind and same judgment (1 Cor. 1:10). Denominationalism thrives on division, different doctrines and names, and is, therefore, wrong. Paul admonished brethren not to call themselves after himself or others because Christ is not divided; it was Christ who was crucified for us, and it is in Christ's name that we are baptized (1 Cor. 1:12,13). We err when we divide and call ourselves after men and points of doctrine as denominations do. In the New Testament, one reads of the church universal (all of the saved) and the local church (the saved in a given locality.) Denominationalism is neither; a denomination is an organization of churches greater than a local church, but less than the universal church. Such organization is foreign to the scripture and cannot be right. Furthermore, denominations often have synods, councils, conferences, etc. that meet to determine their beliefs and practices. This, too, is wrong. We cannot establish church doctrine by vote. Christ is the head of the church (Eph. 1:22); He is the only law-giver. We must look to His scriptures for doctrine (2 Tim. 3:16); they are authoritative and cannot be broken (Jn. 10:35). We should not change them by adding to them nor taking away from them (Rev. 22:18,19; Gal. 1:6-9). We must reject denominationalism and all of its error in favor of the true church and truth.
There is one New Testament church; it belongs to the Lord and is not made up of denominations. When people are saved, the Lord adds them to His church (Acts 2:47), not to a denomination. Christ's church is not denominational.