Atheists, members of cults, and members of most denominations, are quick to point out that the Bible was written by fallible men, all the while ignoring that those men were inspired by the Holy Spirit (2 Tim. 3:16; 2 Pet. 1:21). Not only do they doubt the authenticity of the oldest copies, they are quick to point out that they were also translated into our language by imperfect human beings (there are over 5000 copies of the original Greek manuscripts from all over Europe, Asia, and Northern Africa, that have been found to be nearly identical to one another; and the Dead Sea Scrolls have confirmed the authenticity the Old Testament).
There are several "proofs" that the Scriptures are "God-breathed" (the definition of inspiration):
1) The Bible has been protected throughout the centuries, from those who would destroy it. Diocletian (245-313) tried to do so, but his successor, Constantine, defended it. Voltaire (1694-1778) declared it doomed, but twenty years after his death, his house was turned into a print shop, where the Geneva Bible Society printed Bibles! The ACLU has fought to keep the Gideons from distributing Bibles, but last year, over 84,000,000 Bibles were handed out!
2) There are scientific revelations in the Bible which were not discovered by man until centuries after they were written, such as "the water cycle" (Eccl. 1:7); the Earth is a sphere (Isa. 40:22); the Earth rotates on its axis (six times in Gen. 1:5-31); the Earth is suspended in space (Job 26:7); the atmosphere has weight (Job 28:25); the stars make sound (Job 38:7); life is in the blood (Lev. 17:11); and the Universe is "running down" (Ps. 102:25-26); to name just a few.
3) The Bible is historically accurate. For years, historians have challenged the existence of the Hittite Kingdom, but in 1906, Hugo Winkler discovered the ancient Hittite capital city. Another example is Belshazzar, king of Babylon, was not listed in ancient records, and yet, the Bible says he ruled; come to find out, he ruled in his father's place. Nabonidus, son of Nebuchadnezzer, did not want to rule after his father died, for whatever reason, and so, Nebuchadnezzer's grandson, Belshazzar ruled. That is why he was only able to appoint Daniel to be "third ruler in the kingdom" (Dan. 5:16, 29).
4) Perhaps the most solid evidence that the Bible is God-inspired, is the fulfillment of Bible prophecy. Daniel prophesied that the Medes would conquer Babylon, the Greeks would conquer the Medes, and the empire which would kill Israel's Messiah would defeat the Greeks. Of course, that would be Rome! Speaking of Israel's Messiah, His birth, His life, His death, and His resurrection literally fulfilled hundreds of prophecies!
If the Bible is not true, then no one can be saved from their sin (Rom. 10:9-17)!