That sounds like the Spirit hears and obeys the Church. It is interesting that you say the Spirit does not protect individuals. I see the opposite idea in scriptures:
John 14:16-17 : 16 And I will ask the Father, and he will give you another Counselor to be with you forever— 17 the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be in you.
Rom. 8:9 : You, however, are controlled not by the sinful nature but by the Spirit, if the Spirit of God lives in you. And if anyone does not have the Spirit of Christ, he does not belong to Christ.
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What basis do you use to say that the Apostles taught correctly, but "who knows after that"? Where the Apostles super geniuses? Is God unable to lead people after those 12 supermen died?
Clearly they were not super geniuses. :) The Apostles were transformed at Pentecost. We know what they were like before and after, night and day. It's clear to me that they all received special grace that I presume included correct teaching for God and not for themselves. ... Yes, God is able to lead people after the Apostles died, we strongly disagree on the results of Him doing that.
Jesus made it quite clear that He chooses damaged goods to fulfill God's Will. Consider what Paul says about himself, yet, God worked powerfully AND INFALLIBLY through him.
That is certainly true, however I have no faith whatsoever that God works through today's Catholic hierarchy in any comparable way that He worked through Paul.
Well, that is good that Protestants send missionaries, except that they USUALLY are sent to Catholic countries to conduct proselytism, tickling the ears with false doctrine.
I can't speak for other Protestant churches, but our missionary trips are to places like Eritrea, our last big one. We also sponsor other Baptists who have gone to Sudan. There may be no more dangerous a place on earth for a Christian to be. Everything has to be done underground. Communications are filled with code to protect themselves and the people they are witnessing to. These folks are not looking for Catholics. :) In fact, after any mission trip in our church there is an after-report to the whole church. Not a single time have I ever heard anything like "... and then I met this Catholic and after talking to him, he converted." That just isn't in the picture at all, at least for us.
This is exactly what Christ promised: that whatever the Church binds on earth, He will bind in heaven.
" I can't speak for other Protestant churches, but our missionary trips are to places like Eritrea, our last big one."
I trust its the Mohammadens there you are after and not the Copts or the Roman Catholics.