One of the most common objections I receive from Charismatic Christians when speaking about what tongues is and isn't according to the Bible, is that they have "experienced" a private prayer language, so I cannot tell them that it is wrong and unbiblical because they have "experienced it."
This brings us to the question of ultimate authority. What is the Christians ultimate authority? Is my ultimate authority God and His word, or is my ultimate authority my personal experience? I would think that any real Christian would be ashamed to say "my personal experience is my ultimate authority."
However, even though you'd be hard pressed to find someone willing to admit this, many people act as thought their experience was their final authority. They judge and interpret the Scripture based off of what they've experienced rather than let Scripture judge whether or not their experience is valid.
Such presuppositions lead to false conclusions about what Scripture is or isn't teaching. This is not simply a charismatic issue actually. Many Christians are guilty of doing this regardless of their ecclesiastical background. I'll use the example of Alcohol.
Many Christians consider drinking alcohol a sin, period. Therefore whenever Jesus is said to drink wine, they conclude that it is merely grape juice. This may sound ridiculous to some people, but I know people do it. Their personal convictions regarding alcohol are so strong that they allow their own experience or view point to be the final authority. The truth is that Scripture condemns drunkenness, but not drinking alcohol altogether.
We could list many examples of how Christians can be guilty of letting their own experiences and convictions be their final authority, the point is clear however, we cannot allow this to be so.
Charismatic Christianity has placed such a heavy emphasis on the "experiential" side of things, that the objective word of God is often shuffled to the back. The Bible is very clear about what the gift of tongues is and isn't. But even if you want to contend for a private prayer language, you must do so on the basis of Scripture, if you cannot then you do not have a leg on which to stand.
I've no doubt whatsoever that people have "experienced" powerful, emotional things in their prayer life and worship services. Nonetheless, all experiences should still be subjected to God's word. Should an angel appear to you and tell you to follow another gospel, it may be a real experience, but it stands condemned by God's word according to Galatians 1.
That is an extreme example of course, but should not things like being "slain in the Spirit" and "speaking in a private prayer language" undergo the same Biblical test, regardless of the fact that one may have experienced something. There are many experiences in life that are real but not of God.
So which do you choose to rely on when deciding if something is true and valid to practice as a Christian? Your subjective experience, or God's objective truth?