The Bible is for certain inspired. It is literally the very breath of God transferred to man on paper. It is His love letter to us, His guide book for life, His plan of redemption laid out, the gospel foretold, and truths conveyed in each and every word. All of Scripture is inspired by God. When we move from this belief, it is like building our house on sinking sand. How can we follow a Savior whom we don't think His Word is entirely true and profitable? Believing the Bible is truly inspired by God is based on faith, but it also has proofs backing it up.
There are different ways that people reject the inspiration of God. Most of the people I know that don't believe that God inspired the Bible, believe "parts"of the Bible are true. They don't believe God inspired them and gave them the words to write. They just think the authors wrote the books like any other author. They think of it as just their account of what happened....This belief rejects that the entire Bible is true and can lead to belief that it is instead a mixture of truth, historical documents, mistakes, and allegories.
I think that they hold to these beliefs because they can accept what they want to from the Bible. If they don't like certain verses, they can claim they weren't true. If they are able to convince themselves and everyone else that only certain parts of the Bible are true, then they can pick and choose what they want to accept. If they don't like the fact that God created the world in 6 days, then they can say that that was just an allegory and there was no possible way that God could created the world like that. Or they can justify that God may have used evolution to create the world because they don't believe in the literal interpretation of "day" in Genesis.
Feeling they are not accountable to a Holy God is another reason for rejecting the true inspiration of God. This may not be the reason for all who choose to not believe in verbal inspiration. However, ultimately that is what one can draw from not trusting the inspiration of God. In denying that every single word of the Bible is truth, it provides an escape for following God with complete obedience to His Word. No matter how one reaches the conclusion that the Bible is not the inspired Word of God, then they feel they are ultimately not accountable to God. If they don't believe He even cared enough for them to write the Bible, then how can they trust the Bible? How can they find strength to obey God's commands in Scripture if they believe "parts" of the Bible are true? How can they trust God's promises? How can they share the gospel if they can't have the confidence to know that God wrote out His plan of salvation for us?
He is the Word. He is the life. Satan is out to attack Christians and make them believe that the Bible was not the inspired word of God. If Satan can make one believe that lie, then the gospel, the plan of redemption, Creation, and every promise in the Bible becomes in one's mind nothing more than a nice story. Believing the Bible is the inspired word of God is absolutely crucial in one's walk with Christ.
2 Timothy 3:16. "All Scripture is inspired by God...." The word "inspired" literally mans, God-breathed. How incredible is that!? I can trust what God tells me in His Word about the Bible being totally inspired because I can trust God. He will never fail me. His Word speaks to me and changes my life, and I know He is changing the lives of others through His Word.
Also, the fact that He used 40 people over the course of 1500 years to pen Scripture and nothing in Scripture ever contradicted each other is proof in itself that God breathed the words he wanted to be in the Bible.
“Of the many influences that have shaped the United States into a distinctive nation and people, none may be said to be more fundamental and enduring than the Bible.” -President Ronald Reagan
“We account the scriptures of God to be the most sublime philosophy. I find more sure marks of authenticity in the Bible than in any profane history whatsoever.” -Isaac Newton
It's just absolutely crucial to our faith to know that Scripture is God-breathed. It is His love letter, His guide book for our lives, and every single word is truth. It is reliable, profitable, and is radically changing my life.