The Christian faith stands or falls with the truth of the testimony that Christ is risen from the dead.This is written about the resurrection. It strikes me how similar it is to the problem with Sola Scriptura. That the resurrection makes Jesus the ultimate criterion. He is the one true mediator between man and God. But the moment that mediator leaves this earth we have the same problem again. We are left with merely human authority that is only going to extend as far as it interests us. Unless we aren't. Unless there is an authority on earth that is more than human.
If this were taken away it would still be possible to piece together from Christian tradition a series of interesting ideas about God and men, about man's being and his obligations, a kind of religious world view; but the Christian faith itself would be dead. Jesus would be a failed religious leader who despite his failure remains great and can cause us to reflect. But he would then remain purely human, and his authority would extend only so far as his message is of interest to us. He would not longer be a criterion; the only criterion left would be our own judgement in selecting from his heritage what strikes us as helpful. In other words we would be alone. Our own judgement would be the highest instance.
This is the insidious thing. Protestants claim their authority gets the important things right. So what is the big deal? The problem is that reduces Christianity to something human. You and the thinkers that interest you decide what is important and what are the right answers on those issues. That is the end of the public part of Christianity. The private part of Christianity is still there where we pray and reflect and try and follow Christ. But "what strikes us as helpful" is even more central in our private discernment than it is in our public confession. For me and many protestants I knew that sense is assumed to be God's voice. It can be God's voice. It can also be our own pious imagination. How do we know? We don't. Not unless we have some discernment that we trust more than out own.
Mary is a good example of something that does not interest protestants. There is an assumption that because I don't have a desire to meditate on her role in salvation that it must be unimportant. We read the bible, we pray, we just don't feel led to think about Mary. Is that God telling us she does not matter? Not at all. It is your human tradition becoming an echo chamber and drowning out God. Unless there is an authority that can demand we go beyond what interests us then there is no way out. Then Jesus is not really alive to you. You are still in an entirely human situation.
It sounds harsh. If you reason in good faith and try to follow God why should that not work? But that is why we needed Jesus. People reasoning in good faith was not adequate. He came to give us something better. A new covenant. But we also need a new covenant community. We need to encounter the true Jesus and not just ideas about Him. Even very pious and sincere ideas are not good enough. We need the way, the truth, and the life. Not just from one of the many who claim to have Jesus figured out. From the mystical body of Christ itself.
This is what Bryan Cross was saying with his now-famous Ecclesial Deism article. That Sola Scriptura turns Jesus into "a failed religious leader." Still a very interesting figure but not a criterion. At least not a knowable criterion. No matter how many good things grow from that foundation they are ultimately human things. For we are alone with our judgement. God is not with us.