The author identifies apostasy and moral degeneration as some of the most important signs that a church has ceased to be a church. The author also adds descriptions of what are called cultic churches, whose confessions may go against the faithful traditional confessions of the church as defined by the Word. One example of such cults are those known to deny the deity of Christ; for example, Mormons and Jehovah's Witnesses.
Source: Ligonier Ministries, 2005. 3 pages.