John Knox was a 16th Century Scottish Reformer. His influential theology was profoundly biblical. In this short video, I analyze his Biblical argument for the position that the Roman Catholic Mass is idolatry. What we find is that the argument Knox uses to show that the Mass is idolatry also applies to many worship practices that contemporary churches are engaged in each and every week. Take a look at what Knox had to say and see whether he would consider any practices in your church services to be ‘idolatry’.