Michael Liccione and Scott Carson have extended the discussion about the 'plain meaning of Scripture' by considering the matter in light of my recent suggestion on the subject. Both are worth reading. There's also some good discussion in the comments of my post.
I've decided that I wanted to explain why I jumped into the discussion (besides knowing it was a good one, given that I've interacted before with a number of people discussion the matter). I think there is a common Catholic tendency to conflate a number of questions when it comes to this subject; and, in particular, a tendency to diagnose 'private judgment' too early. Contrary to what you might think from reading some Catholics on the subject, very few Protestants, even Baptists, advocate private judgment as such even if there is good reason to think they make interpretation of Scripture a matter of private judgment in effect. Thus Catholics need to be careful about how they interpret things Protestants say that sound to them like an advocacy of private judgment. The reverse is true, in fact, and one reason I take the issue seriously is that I've seen exactly the same sort of mistake made in reverse: Baptists reading Catholic accounts of Scripture as denials of Christian liberty. Of course, this is absurd; what it amounts to is a conflation between Scripture's account of the liberty of the Christian and Baptist views of Scripture and ecclesiology; but no matter how relevant one of these is to the others, they are distinct questions and moving from one to another requires looking at different principles.
One can even imagine a dialogue going like this between a Baptist and a Catholic.
C. The problem I have with the Baptist approach to Scripture is that it makes Scripture a matter of private interpretation.
B. I don't understand; I would reject any such claim.
C. But don't you hold that Scripture has a plain sense, and that this plain sense alone is authoritative, independently of the Church?
C. And that to interpret Scripture properly all you have to do is read it?
B. As long as you aren't willfully misreading it, or letting unscriptural biases get in the way of reading it plainly, yes.
C. Isn't that private judgment?
B. No; it's simply the claim that Scripture was written for plain people, and its message for the world. When Paul wrote letters to the churches, he didn't tell the people he was writing that they needed some authority to tell them what Paul said. Instead, we find he says to the Ephesians (3:4), "In reading this, you will understand." And he says this about an extremely important topic, the mystery whereby the Gentiles are made participants in the promise of Christ.
C. But you are still taking it on yourself to interpret Scripture by yourself. That seems to be private judgment.
B. It's 'private judgment' in the sense that you yourself are reading Scripture and seeing what it means. But this is what everyone does. No one condemns the men of Berea for searching the Scriptures daily to see whether the word being taught was true. Rather, we consider them to be noble for it.
C. But consider alternatively the example of the eunuch from Ethiopia, who wished to understand but could not unless some man should guide him.
B. Yes, indeed; but this simply means, at most, that the gospel must be preached; salvation generally comes through hearing, so to speak. And there is obviously a role for teachers to help people come to better understanding of Scriptural passages. But it does not follow that every Christian must be guided to every little bit of edification from Scripture by others. The things we find in Scripture were proclaimed to ordinary people, and they understood. They did not go to the bishop and ask, "How are we to understand this?" You can call this private judgment, if you like, but it's hardly a problem for plain people to use their minds.
C. I agree there's no problem with plain people using the reason God gives them; I would encourage them to use it more than they usually do. But here's my problem with what I take to be your view: Scripture has an authority that you do not; but your view means that we never have the authoritative meaning of Scripture, only everyone's opinion about what it might be.
B. Scripture certainly does have authority. But, on the contrary, this requires my view; for it is Scripture itself, not the interpretation put forward by a bishop, or by the Councils, that overcomes the heart and takes hold of the conscience, producing in us a deep conviction of our need for God and His Christ. And, in fact, we cannot recognize the Church Fathers, or the Councils, or any bishop as having authority in these matters except insofar as they can be understood as saying things consistent with the meaning of Scripture.
C. But, again, when you say 'Scripture means this' you really mean 'I think Scripture means this'. You have no special authority to say what the authoritative sense of Scripture is.
B. I would concede that, in the sense that I can't put forward the meaning of Scripture on my own authority but only point to it as something that rests not on me but on God. You must understand that when I say that Scripture alone is the rule of faith, I mean it seriously. What has authority is not the Word of God understood by any old fool like me, but the Word of God as holy men of God wrote them under the inspiration of God. And all that I do when I talk about the meaning of this or that Scriptural text is to direct people to the text, each of them to face the Word of God on his or her own, thereby to be convicted and edified. To be sure I, like everyone else, am fallible. But the Word of God is not; it is truth spoken by Truth.
C. But you still think that every person has the right to read it for himself and make his own decision about it.
B. Yes, just as every person who came to hear Jesus heard for himself and made his own decision about it. But this, in fact, is why I deny that Scripture is simply a matter of private interpretation: we must not bring our own private meanings and opinions to the word, but must let ourselves be faced with the word of the Holy Spirit. You see, this is the problem I have with the Catholic view of Scripture: you simply don't give Scripture enough credit.
C. How so?
B. If there is one thing that is clear, it is that Scripture is an instrument whereby God moves hearts and minds. We Baptists hold that it is God who works through Scripture. But you Catholics are always trying to put men in between Scripture and its readers: listen to this man, listen to those men, they'll tell you what Scripture says and what God is saying to you through it. But this, in the first place, replaces the teaching authority of God with the teaching authority of men; and, in the second place, it is a complete rejection of the freedom we have in Christ. With regard to the first, Scripture stands over against us, the word of God, the means whereby God exerts his authority over us and moves us to faith and hope and love; it is a way in which God confronts us. With regard to the second, you forget that each Christian participates in the life of Christ, and that because of this we are a royal priesthood, a holy nation, each of us with access through Christ to the throne of God, and each of us able to be edified by the words of Scripture.
C. I don't deny either of these things; what I affirm, in fact, requires both. It's just that the Scripture that stands over against us as God's word is the Scripture as preached, practiced, and prayed by the Church. Anyone who does not read Scripture as such is precisely the sort of person who is bringing his own private meaning or opinion instead of letting themselves by faced by the truth presented by the Holy Spirit. And I certainly don't deny that every Christian may freely come, in the Spirit of Christ, to Scripture to be edified. But this is precisely because we do it as a 'royal priesthood, a holy nation' called forth to praise God: that is, because it is one of the things we Christians do as members of the Church, of the Body of Christ, even when we do it individually, because we can only do it properly in the Spirit of truth. And this requires coming face to face with Scripture, not as a dead text but as a living and active instrument of God, with the power to build us up and give us our heritage. The Church exercises its authority not as standing in judgment over Scripture, but as serving it, guarding it zealously and teaching its meaning in the Spirit of Christ....
And so forth forever, with each attributing to the other things they deny, and each denying that they believe what is attributed to them, at least in the way it is attributed to them. Actually, this topic, I think, is a good argument for the rule that Christians should never engage in apologetics against other Christians without first explicitly going through all the things relevant to the topic that the other side gets right; we might have fewer of these very nonconstructive jumps from one claim to another, whereby denial of private judgment is taken to be affirmation of a Magisterium, or the affirmation of the teaching authority of Church is taken to be a denial of Christian liberty. Things are not so simple. And that's why I felt I had to jump in and say something.
In any case, I do recommend reading the posts by Scott and Mike that are linked above.