What is the purpose of language? This really is a no-brainer. The purpose of language is to communicate a thought between one person and others. For example, if you came to visit me and wanted to know where the nearest corner shop was, you could ask me, and I would know where you wanted to go. Then, I could tell you how to get there, and you would know also. I could even write down some directions for you so you can't forget on the way.
As it turns out, God has quite a few thoughts He would like to share with us, and He has provided them for us in book form via His divinely inspired messengers. God, as the inventor of language, is rather capable of using it. Therefore, His word is useful doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work.
"Not so", say far too many Christians. According to them, the Bible is wide open for interpretation. Conveniently, this allows them to read their own previously held opinions into the Bible, rarely, if ever, learning anything from it. But if the Bible is so wide open for interpretation, why do we even have it? If it's so pathetically ambiguous that it says one thing to me, and another to you, what's the point? Answer: Because it isn't open to interpretation. The Bible has a fixed intended meaning. Therefore, when two people disagree on what that meaning is, at least one of them must be wrong.
Let us take the obvious example of origins. Theistic Evolutionists, and others with similar views, argue that they are not actually disagreeing with the Bible. They are merely disagreeing with Creationist interpretations of the Bible. Creationism and Evolution are mutually exclusive. They cannot both be right, because that would require multiple opposite statements to be true in the same sense at the same time, which is the very definition of a contradiction. Therefore, either Creationists are right, or Evolutionists are right.
Having already explained why the multiple interpretations thing is positively asinine, let's ask which view fits the (very much unambiguous) text better? The first thing that tells us the Creationist view is more compatible with the text is that we actually use it! Our view is not only based on the text, it is the text. We believe God created the heavens, earth and all that is in them because Exodus 20:11 explicitly says "For in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day." We believe Adam was the first man because the Bible explicitly says "And so it is written, “The first man Adam became a living being.”" (1 Corinthians 15:45, cf Genesis 2:7). We believe all people are descended from two people because the Bible explicitly says "And Adam called his wife’s name Eve, because she was the mother of all living." (Genesis 3:20) and "And He has made from one blood every nation of men to dwell on all the face of the earth" (Acts 17:26, some translations say "one man" instead of "one blood").
I could go on, but suffice to say, Creationism is based on the text. If God wants us to be Creationists, He could not have said it any clearer than He does. By contrast, if He wanted us to be Evolutionists, or even Old Earth Creationists, there are many ways He could have been clearer. Indeed, the majority of the Theistic Evolution case stems from disputing how literal the text is. In other words, whereas Creationists can defend our interpretation just by reading the text, Theistic Evolutionists must admit "well, yes, that's what it seems to say, but we believe it means this, because...". That "because" is always followed up with some external, usually very secular source. The text is not compelling them to accept Evolution. Rather, they are imposing Evolution on the text because they already believed it.
Origins is far from the only example. Indeed, it is a sad fact that in our day and age, there is not a page of scripture that isn't being treated like someone's personal notebook. Alien interpretations are being imposed on the text left, right, and centre. Some try to impose their own immoral view of sexual ethics on the text. Some try to cram the prosperity gospel in there. Every heretical denomination on the planet hides behind the multiple interpretations defence. The Bible is a battlefield, but it simply shouldn't be. It ought to be the weapon!
And it is, for the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart (Hebrews 4:12). That's why the devil and his goons don't want Christians learning how to use it. If people would just faithfully study the Bible, we would not see the House of Christ so pathetically divided against itself. Instead, we would see an army of well trained warriors destroying the forces of darkness, and spreading the Gospel to the world. Therefore, do your part, and take Paul's advice to Timothy: Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth. (2 Timothy 2:15). Let's have no more of this "interpretations" nonsense.