In our day [1889!], people either do not make this distinction at all, or at least not in the right manner. They not only fail to declare it the Christian’s duty to distinguish between orthodox and heterodox church bodies, but they even declare it to be a Christian virtue when people pay no attention to the doctrinal differences. Yes, they call it presumptuous when a church body maintains that in all articles of Christian faith it has the revealed truth of God’s Word. We are ridiculed… because we make a strict distinction between orthodox and heterodox churches.
Excerpt from The Distinction Between Orthodox & Heterodox Churches, Thesis III.