William MacDonald defines the local church as a community of believers gathered in Christ's name, emphasizing that true churches are not merely defined by rigid requirements but by their spiritual condition and unity in Christ. He argues that the local church should reflect the universal Church, embodying truths such as the oneness of the body, Christ as the head, and the role of the Holy Spirit. MacDonald stresses the importance of love and grace in maintaining unity among believers, warning against the divisive nature of denominationalism. He calls for a church that represents Christ faithfully, avoiding sectarianism and promoting genuine fellowship among all Christians. Ultimately, the local church's mission is to testify to the unity and holiness of the body of Christ.