Following Bryan Cross' 10 (12) questions for Protestants, I'd like to ask one more (and this one, I'm unable to come up with a bad answer like I did for Bryan's).
To start with, step back for a second and just look at the history of the Christian religion as a whole (step out of your current mindset for a second and just look at Christianity objectively with no leaning towards any particular denomination or way of seeing Christianity in so far as you are able).
Now I would like to know which Christian world view would allow for a Church (be it invisible or just the collective body of Christians) that was almost completely in grave error for her entire existence? (Let's assume one could prove such a thing...for the sake of the argument). Put another way, if we were to find that nearly all of Christianity had been wrong about extremely important theological issues, what kind of Christian world view would allow for such a thing? If yours does, then how? That is my question, how/why did God let almost all of Christianity - the new chosen people to reveal Himself to the world - get everything so terribly wrong?
Would God have allowed Noah to build a faulty ark? Now how about Israel? We all know they were many times a poor representation of what God intended for them. But we see they went astray and were corrected - they returned to orthodoxy. As many times as they strayed, God disciplined and brought them back. Now isn't this the model for the Church? But the Protestant model is that the Church went astray and God did not correct them but rather raised up 'Spirit filled' leaders to start a new one (or however you want to re-word it).
At this point, I'll concede a bit. I will assume for the sake of the argument that the "Church" somehow isn't specifically the visible Catholic Church. We will just say that it is the invisible collective body of all true Christians everywhere. We are still left with the above problem. If we assume (and remember we already have) that one could demonstrate the vast majority of Christianity to be in grave theological error over the centuries, how can we make sense of such a scenario? Doesn't it strike you as theologically incoherent? If not, explain how this makes sense.
In such a scenario, I think we would be forced to view the "Church" as the tiny minority of Christians throughout the ages. Sure the "Church" existed in the first few centuries even as the majority of Christians were starting to gradually fall for 'popery'. But we're talking a small handful of people and even today - even conceding such a scenario I'd be unwilling to accept the "Church" being anything other than a tiny fraction of Christianity.
Now I would like to hear Protestant answers GIVEN those assumptions. (Remember we must assume that the vast majority of Christians were in serious theological error throughout the ages) now I want to hear the answer to that question.
But we are making some rather hefty assumptions aren't we? So let me back them up. For 1500 years, the entirety (100%) of Christianity believed in Transubstantiation. This is simply an objective fact. For the last 500 years, Catholics and Orthodox maintain it (and they make up by far the majority of Christianity) So if we were to just look at all of history objectively, we can see that the huge majority of Christianity believed in something that, if wrong, is gravely wrong. This is but one (albeit most likely the strongest) proof for the above assumptions.
We should also be aware that there are several other issues we could bring up as well - apostolic succession, rejection of sola scriptura & sola fide, infant baptism (certain Protestant denominations accept this, only making the remaining denominations even smaller fractions of Christian majority on this issue) and several other issues.
So let's assume for the sake that one particular Protestant denomination is correct about everything. Let's pick one and see- I'll use PCA since that's what I come from. If the PCA theology is correct, that makes mainline Protestants wrong on several very important moral issues. It makes most Baptists wrong on salvation (at least mostly wrong), it makes Methodists wrong on "Perseverance of the Saints" and it sure as hell makes Catholics & Orthodox wrong about a number of things (we needn't go down the list but we could list out very serious errors of all other types of Christianity such as the ones we already have).
In this scenario, we have a tiny fraction of modern Christianity being right and the huge huge majority of it being wrong on a large number of very serious theological issues. Sure, lots of Christian denominations would be close enough not to be called Pagans, but the vast majority of Christianity still holds one or more serious theological errors including (but not limited to): falsely worshiping the created as the Creator, illicitly communing with the dead, rejecting infant baptism, rejecting the Total Depravity of man or one of the other five points of Calvinism, rejecting sola scriptura and or sola fide as taught by the WCF etc... Now ask yourself, is this scenario plausible? Ok so you're not comfortable with using the PCA. Replace it with any denomination you choose. Is it a plausible scenario? The answer is no. We all know it's not. But, if you disagree, then by all means, explain why that scenario is plausible.
But suppose we used the same scenario and replaced PCA with the Catholic Church. Is that scenario plausible? I think the only reasonable answer is yes. It is a plausible scenario (forget the details for now, don't start objecting because of the pope or Mary or something else) the scenario itself is quite plausible. If not, then I want you to explain why it's not (without talking about any specific doctrinal disagreements, remember we're not getting into specifics of who's right and wrong on any certain issue - we're just looking at which scenarios are plausible and then we can weigh our options). As a footnote, I would also agree that the scenario would also be plausible by replacing the PCA with any one of the Orthodox Churches.
I think it is utterly logical that Christ would establish the Catholic Church (which alone constitutes the majority of Christianity at any point in history even up to this very day and for the first half of Christian history constituted 100%) as the true and full heir to the nation of Israel. I think it quite reasonable that He would act towards her in a similar manner as He did with Israel (that is, never abandon her, always correct her when she goes wrong and brings her back). I don't think it's hard to believe at all that instead of the Catholic Church being wrong it is the fraction of Christianity which by doctrinal novelty disagrees with her that is. So again, I don't know of any way to say such a scenario is implausible. If you think the scenario is implausible, then explain to me why.
So my conclusion with the above assumptions (given that these arguments are true) we are left with an outlook on Christian history where it would be implausible to say any given Protestant theology is correct and only the Catholic or one of the Orthodox Churches could possibly hold true.
So if you want to contradict me, let me summarize. The only way to deny the above conclusion is to show that either A) it would be plausible for the Holy Spirit to leave the huge majority of Christianity throughout the centuries to their own devices (and watch almost all of them be wrong about serious issues) or B) prove that the majority of Christianity has not been in serious error over important theological issues. (And to avoid the "its possible to be wrong on some but right on others" argument, just start with Transubstantiation).