There are certain phrases that are meant to put us at ease by some Bible teachers, and disarm us from being too critical of a particular interpretation in terms of how faithful it is. Some phrases exist to sneak in ideas that ultimately reject the teaching of the Bible while at the same time explicitly affirming a faithfulness to what the Bible teaches. Let's talk about one of these today.
The phrase, "the Bible interprets the Bible" is something I hear quite a bit these days, and like most bumper sticker theology, it's an idea that is widely misunderstood. What most people think this means is that we just harmonize all texts together, as though the entire Bible is the context for a particular word or phrase. But that, in my estimation, skips a vital step in being linguistically responsible with language and letting context speak for itself.
The canon certainly is the context of the books therein, but the immediate contexts have to be considered first and then branched out from there. Otherwise, one can, and often does, replace the actual context of something that is said with a foreign context, making it say something completely different than what was intended by the individual author of that particular book in the Bible.
Context is king when understood to grow out from the smaller contexts to the larger. So, for instance, I understand that John uses the word pneuma in John 3:8 in two different ways, precisely, because I start at the micro-context before placing it within its macro-context of the entire canon, or even the Gospel of John as a whole. At the clausal and paragraph level, I can see that one use of pneuma refers to the Spirit of God/Holy Spirit, and the other refers to the wind. The other words that form its context in the sentence (e.g., blows, hear the sound, where it comes from, where it goes, etc.) informs the reader that literal wind is in view. But the larger subject at the paragraph level informs the reader that the other use of pneuma here speaks of the Holy Spirit who causes a spiritual rebirth by which men who are now born of Him speak and conduct their lives.
Indeed, this then connects to the larger theology of John in his Gospel that teaches us about the necessity of the regeneration of the Spirit and that such cannot be seen physically, since true worshipers are those who worship God through the Spirit and truth, rather than through their physical ethnicity.
We can then apply this teaching to the larger teaching concerning the Holy Spirit and regeneration throughout the Bible as its larger context that shows us the Word and witness of those born of Him.
But what if I looked at all of the texts that deal with wind in the Bible and concluded that these must be the immediate context for the word pneuma? I would see that the word is often used for the wind of God that looks much like a storm. I would have to conclude that this refers to a storm, and that this is really talking about being born from the storms of life, which are trials. Now I just turned what was a theology of unconditional election and the regenerating (monergistic) work of the Holy Spirit into a works-based reward system for those who persevere through trials in life and yet still obey God.
This is what happens when one ignores how language works. The "Bible interprets the Bible" credo does not mean one rips two passages out of context, strings them together to provide a totally new context for each, and suddenly we get what God meant by all of it. What it does mean is that we interpret each text within its own context, then look at the larger section of the book, then the larger book, then the group of books by that author, then other books of that genre, then section of the canon, then the canon, all passages being taken within their own contexts first and then brought together to complement and often restrict our thinking concerning the subject matter.
That takes language seriously, and we ought to take it seriously because God used it to communicate to us His truth.
You can do this with anything, and people often do. Cults do this all the time. Try and get a JW to stay on one passage at a time. Good luck. If he does that, he loses the debate. By ignoring the immediate context one can make a passage say anything by using other Bible verses as their context, and so cults love doing this because they can support whatever heretical theology they desire by such a faulty methodology. Liberals go the other way and never bring the actual teachings of the passages and books together--this largely due to their presuppositions concerning what the Bible is as a human book about God rather than a divine book written through humans. But this does not justify a sloppy reading where we mesh everything together while ignoring the actual context in which it is said.
Try this with the word "world" in John's writings. By the end of it, one will have God loving the wicked practices and thinking that is hostile to Him. Try it with the word "flesh" in Paul's writings. By the end of that reading, one will have to conclude that Paul lives in the flesh by faith in the Son of God, which he tells us that those who live in the flesh must die and do not know Christ.
Absurdities are multiplied when we ignore how language works. In fact, I would change the phrase completely. The Bible does not interpret the Bible. An interpreter interprets the Bible using either a good or bad methodology of understanding the language used in context, along with understanding what contexts need to be considered primary. But the Bible does not interpret individual passages or books for us. The Bible teaches us the whole counsel of God on a subject and it does so by teaching us individual elements of that subject in every context first. It teaches us a larger theology and ethic through the books that then can be put together in a display of the continuity it has with itself. But one part of the Bible does not interpret another part. The immediate context of the passage and book provides what is needed for interpretation. The Bible supplies the missing elements of the whole counsel of God that an individual passage or book does not possess within itself, and so must be joined to the rest in order to fill out the bigger picture.
So no more of this sloppy prooftexting, where one runs around the Bible when a context doesn't provide the interpretation he wants. It is simply another way of rejecting the Bible, even while explicitly affirming one's faith in it.