The Bible Claims to be the Word of God
More than 2000 times the Bible claims to be the Word of God. This is seen both in the Bible quoting the words of God directly,
"Then God said to Noah, "The end of all flesh has come before Me; for the earth is filled with violence because of them; and behold, I am about to destroy them with the earth." (Genesis 6:13)
...God speaking through the prophets,
"Then the LORD stretched out His hand and touched my mouth, and the LORD said to me, "Behold, I have put My words in your mouth." (Jeremiah 1:9)
...and in the inspired apostles and prophets
"But know this first of all, that no prophecy of Scripture is a matter of one's own interpretation, for no prophecy was ever made by an act of human will, but men moved by the Holy Spirit spoke from God." (2 Peter 1:20-21)
"For this reason we also constantly thank God that when you received the word of God which you heard from us, you accepted it not as the word of men, but for what it really is, the word of God, which also performs its work in you who believe." (1 Thessalonians 2:13)
The Claims Substantiated
If the claim that the Bible is God's word can be substantiated (and I recognize this argument is still conditional) then the existence of God is no longer an open discussion. The question then is not whether there is a God, but is the Bible the word of God, as it claims to be. For the record, I believe that this claim can indeed be substantiated by the many prophecies, miracles, and by the resurrected Christ.
Millions have staked their lives on the words of the Bible. And while there is a strong argument to be made that they wouldn't risk life and limb for a pack of lies, there is a stronger argument to be made by examining the evidence. This conditional and dependent argument - that God must exist because His word exists - serves as a springboard to launch us into the study of the Bible as a reliable and divine work.