Totally reasonable/good question(s) here! This is such an important thing to wrestle with and to ask ourselves...

Let me try and speak to the various points you raised in your questions, the first being: Why consider the bible to be authoritative?

Let's move the way knowledge naturally progresses—from what is clear to what is unclear. So what is clear? Well, I would argue that Jesus is the clarity that we can use to understand why Christians have always believed the bible is "inspired by God." Historians agree that Jesus was a real human being who lived and taught in first century Palestine and that he was executed by crucifixion. We have numerous sources outside of the new testament that confirm this. We also know with certainty that Christianity rose in the 1st century among monotheistic Jews. So historians are left with this conundrum of how Jewish folks who all held a strong, deep-seated religious conviction that there was one God and that anyone who was hung on a tree was cursed began to believe and to preach that a man hung on a tree was actually God in the flesh... what's more, they had nothing to gain from this other than persecution and death. Many scholars have come to believe, in spite of our inherent naturalism, that outside of the belief that Jesus was literally resurrected from the dead, there is no way to explain the rise of Christianity in the first century.

So some begin with the historical dilemma of the resurrection and they work backward to the gospels and apply the same historical scrutiny to them that they would any other historical document and discover that they stand up to the criticism—and tons of volumes are being published on these findings (The Resurrection of Jesus by Mike Licona, Christian Origins and The Son of God by N.T. Wright, The Jesus Legend by Greg Boyd and Paul Eddy to name a select few). And I'm speaking here to the historical method for authenticating an ancient document, NOT to confirming it as "inspired by God." Once you have a historically sound document and a historical case for the origin of the Christian faith, you have, at its center, a dude who endorses the Old Testament and claims that scripture is authoritative/inspired by God. So for some of us, the evidence leads backward to faith, as opposed to blind faith leading forward into scholarship, if that makes sense.

Christians believe that Jesus' resurrection from the dead affirms his teaching as true. Paul himself said that if Jesus has not been raised from the dead, then everything we believe is a lie. If we are to take Jesus and what he said seriously, there's no escaping the fact that Jesus believed the Hebrew scriptures were God's word.

So, I have to take issue with your quote, "(the bible) is only Scripture because some people decided it should be scripture." I would argue that this is not actually the case. The Hebrew scriptures have been held as authoritative for thousands of years and confirmed to be as such by Jesus himself, who Christians believe is actually Yaweh (God) come in the flesh.

The Gospels were spread via oral tradition before they were committed to paper, and many scholars and historians have done great work in arguing for the integrity of oral tradition. Other areas of the New Testament are made up of letters that we've discovered copies of. We have New Testament manuscripts written within a couple of generations of the originals, whereas with other ancient texts anywhere from 5 to 10 centuries elapse between the original and the youngest surviving texts. Moreover, only a few major religions have texts claiming to be "God's word." Hinduism and Buddhism, for example, don't claim to have infallible texts.

So, while it is true that the canon of the bible (that is, which books/letters are included as authoritative/inspired) was in a sense "decided upon" by human beings, the inspired works of the new testament were received as such by Jesus-followers almost from the start. The vast majority of New Testament canon was settled by the second century, and over 90% of the new testament can be reconstructed from quotes of the early church fathers up through the 3rd century. No one was even terribly concerned with an "official" canon until this dude called Marcion comes along in the 2nd century trying to canonize a wacky volume on his own. Marcion was an anti-semite who thought an evil god wrote the old testament, and church fathers felt the need to respond to his weird movement when it gathered some steam. Thus, they put together an official teaching on what was and was not the true new testament. Not that the New Testament hadn't been formed until then, in fact, the first known "official" list dates about A.D. 170, and it's nearly identical to the list used today.

In the wake of zany (and completely laughable by scholarly standards) internet videos like Zeitgeist, and popular fiction that folks like Dan Brown are cranking out, this idea has surfaced in modern culture that there are all these "bible books", and some council tons of years after the rise of Christianity sat in a circle and arbitrarily decided which books to include and which to throw out, and this is simply not true.

There is an incredible historical credibility preserved in the New Testament—which, from cover to cover, venerates a man who held the Old Testament as God's inspired word.

For over 2,000 years, Christians have believed and taught that the bible is infallible and inspired by God. Logically, if you hold the bible as simply a book of insights (as many do) you inevitably throw out Jesus' divinity and are left with an ambiguous book of mystery which is, at best, tainted by human error and at worst overflowing with outright fabrications. Why then, would anyone follow the man presented in this book who literally claims to be God and who teaches that scripture is divinely inspired? How can we? Which areas are reliable and which areas are not?

It's true that there is some debate among evangelical Christians over whether or not the word "inerrant" (without error of any kind) or the word "infallible" (never wrong in matters of faith and practice) best suits the bible. Some folks believe that though the bible is never wrong in matters of faith and practice, it does technically contain some scientific errors and minor discrepancies as a result of human authorship, but ALL Christians affirm that any alleged errors of science or numerical inconstancies have no bearing in matters of faith and practice, and are clearly identifiable. For example, ancient people seemed to believe that the world was held up by pillars and surrounded by a hard dome that kept the waters they believed were above the earth at bay. This is not scientifically accurate, but God need not make this clarification in order to effectively communicate through his divinely inspired author.

Some argue that nitpicking the alleged "errors" in the bible is tantamount to the liberal theology of holding the bible as a largely mythical book with some good insight in it. But as I mentioned, none of these alleged errors have any bearing on fundamental areas of belief, and some Christians even believe that these errors are not without reasonable explanation that would render the text errorless, or "inerrant" as they say.

So basically, if you don't hold that God inspired the bible, as you've mentioned, then i would say absolutely, there is no good reason to consider it as authoritative and to emphasize it. I would also argue, then, that you may be in a pickle affirming Jesus as God and believing in his teachings, and you're then faced with the issue of the historicity of the Gospels, the dilemma of the rise of Christianity in the first century, and basically figuring out what it is that you do believe about Jesus… Sadly, Jesus leaves us no option of holding him as simply a cool teacher, since he made bold and devastating claims to be God and to demand Lordship over our lives. For better or worse, Jesus is either a liar and thus not a very good teacher or person at all, or what his first followers believed is actually true: everything he said is true.

If this is the case, then the bible is truly inspired by God and is a living, moving, life-giving text and Christians have been right for thousands of years in holding it in the highest of authoritative places. This is why Christians emphasize the bible, and I would argue, rightly so! It is God's word to us!

We just have to decide whether or not we agree with them.

In affirming the bible as God's inspired word, I, personally, have found an incredible power in its scriptures. My passion for the bible is not motivated by fear or by indoctrination, but out of my love for Jesus and my sincere belief that he is King, and that everything that he said is true.

What do you think? -Josh