The Bible never tries to prove the existence of God.  It starts with the statement, "In the beginning God ..."(1) and later says that everyone knows there is a God - although we often try to suppress this(2).

This doesn't mean that belief in God is irrational.  In fact, there are many rational arguments for God's existence.

However the Bible reveals much more about God than can be deduced intellectually.  It tells us that he is a living personal Spirit, and tells us about his glory, his lordship, his holiness, and his love.  The Bible also presents God as three distinguishable persons: a trinity comprising the Father, Son, and Holy Spirit.(3)