Of the Church, XXV:5

The purest Churches under heaven are subject both to mixture and error; and some have so degenerated as to become no Churches of Christ, but synagogues of Satan. Nevertheless, there shall be always a Church on earth to worship God according to His will.

In this world, even the purest of churches are not guaranteed to be or remain 100% pure. Augustine of Hippo used the phrase corpus per mixtum, a mixed body, alluding to our Lord's parable of the wheat and the tares. God knows his people and is able to sort them from the false professors.

Some churches are not only not pure, they have degenerated to the point where they are no part of the Church but are instead "synagogues of Satan." The language is strong but appropriate. In this day, one can cast an eye over the theological landscape and readily identify churches that once upheld the biblical gospel but now are a tool for the spread of error and deception. They have "Ichabod" written over their doors.

It is even possible that the total state of the Church in this world may fall upon such hard times as almost to disappear. But our Lord has assured us this will never be the case. God will always have his witness and his worship.

Tomorrow: The true head of the Church.