How do we know that there is one church?

The concept of one church is rooted in the teaching of Scripture, particularly in Ephesians 1:22-23, where we read that Christ is the head of the church, which is His body. This emphasizes that despite the existence of many local congregations, there is fundamentally one church made up of all believers united in Christ. Additionally, Ephesians 4:4 asserts, "There is one body and one Spirit," indicating both unity in the church and the singularity of God’s Spirit among His people. This understanding encourages believers to recognize unity beyond denominational differences, focusing instead on shared faith in Christ as the cornerstone of the church.