"For we can do nothing against the truth, but [only] for the truth."
Those churchmen who are faithful in their rightful callings: be they as apostles (as per Paul, we have them no more); or as ministers; or as other church officers; or as believing parishioners--cannot do anything "against the truth," but only "for" it.
How is this possible? Doesn't this seem preposterous? It is possible, and true because of the superintending work of God Himself, keeping His children in the fold, and in the faith. If you live by faith today, loving Christ--do what you will. Whatever you do will please God (because of Jesus' sacrifice); and it will forward the truth of the gospel.
[Puritan quote of the day: "Peter at one time believes and walks, at another time he doubts and sinks, (Matt. 14:30)." --Thomas Brooks, in "Heaven on Earth"]