‘We know that there have been periods in history when the church was more or less pure. But it has always been what St. Augustine described as a corpus per mixtum, a mixed body. Our Lord described the church as an institution that included both tares and wheat. Sometimes the tares gain the upper hand and lead the church into apostasy. Some churches have degenerated to such a low degree that they cease being churches at all. But no church in any age has been utterly pure. It was the clergy who gnashed their teeth in hatred of Jesus and plotted His death. It was the church that condemned Luther, banished Calvin from France, and dismissed Edwards from Northampton.’ R.C. Sproul.
“Dear Bob” Tabletalk Magazine. 1 Apr 1992.