Bavinck ( Reformed Dogmatics: Abridged in One Volume ) has this helpful discussion of the meaning of “true” in Protestant ecclesiology: “A true church in an absolute sense is impossible on earth. For that matter, neither can a wholly false church exist; to qualify for that description, it would no longer be a church at all. The Protestants, though firmly rejecting the church hierarchy of Rome, continued to fully recognize the Christian elements in the church of Rome. However corrupted Rome might be, there were still left in it ‘vestiges of the church,’ ‘ruins of a disordered church’; there was still ‘some kind of church, be it half-demolished,’ left in the papacy.” These all come from Calvin.

Given this complexity, “the Reformers warned against absolutism and arbitrary separation” and began to make “an important distinction . . . between a ‘true’ and a ‘pure’ church, with the former not understood in any exclusive sense but as a description of an array of churches that upheld the fundamental articles of Christian faith while differing from each other in degrees of purity. ‘False church’ became the term for the hierarchical power or superstition or unbelief that set itself up in local churches and accorded itself more authority than the Word of God.”