God's existence is never questioned in the Scripture, for the Biblical agents took His existence as an indisputable fact.  In fact, the agents never sought to define God.  He is described in many passages, but never defined.  The Buddhists would define God as "the Nirvana, the source of all".  But Jehovah God is never defined, but described through His characteristics.  In fact, the best description of God is found in:

Exodus 3:13-14 "And Moses said unto God, Behold, when I come unto the children of Israel, and shall say unto them, The God of your fathers hath sent me unto you; and they shall say to me, What is his name? what shall I say unto them? And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you. "

With these words, I AM THAT I AM, God's sought to explain His infinite nature to finite men.  In the Hebrew a person's name expressed his character.  The title that God gave Himself for man's use was I AM THAT I AM, YHWH, meaning "I am, have always been, and will always be. I exist through Infinity".  I AM THAT I AM denotes God's position that He was never created by men, that He was not formed as a creative release for scientific ignorance, that He has never been nor ever will be a figment of our imagination.

To say that man created God is to defame the great I AM.  Man did not create God to cover up his ignorance of nature. This can be proven historically.  If Joseph did not understand that the virgin birth was contrary to nature, then why did he seek to give Mary a divorce quietly so as to spare her death by stoning?  If men did not know that the sun normally rose in the East, then why would they have been interested in its rising once in the West, a sign of Christ's coming?

(C. S. Lewis) "The religion in the world today gives its followers the greatest happiness is, while it  lasts, the religion of worshipping oneself..."

Man has sought to take the place of God ever since the tower of Babel.  The attempt to defame the  Bible as a work of men is but one facet of this revolutionary conspiracy; out and out atheism is the other facet.  But one problem that the atheists have is that God left His signature on what He created.  He did this so that no logical thinking person could disbelieve that there is a Creator God.

In nature there is a pattern, a design, a system of order for all things.  If, as the atheist claims, all things just happened out of chaos, then this order would not exist. The child is always genetically marked by the parent.  White parents have white children, just as black parents have black children. This is the order of nature. You cannot have order out of chaos, for chaos creates chaos.  Nature, too, is genetically marked by it's Creator.  Had nature come out of chaos, then there would be no order or apparent design.  As nature has order and design, this demands that its Parent be intelligent.  The Parent of nature must logically be God, just as the parent of the black child must logically be black.  There is no other choice.

Another point is the effect of nature.  Nature itself is not an effect, so what is it's first cause?  Science can explain the links in nature that lead to an event, but science cannot explain the first cause.  They do not know nor can they prove the beginning of the link.  The reason that the chain is there at all is a mystery to science, but not so to Christianity.  As C. S. Lewis stated:

"The law of physics .. when one pool ball (A) sets another pool ball (B) in motion the momentum lost by (A) is equal to that gained in (B). This is the law. But this is only provided something sets (A) into motion. The law does not set the ball into motion ... but if on a ship with the pool table, and the same occurred, it was not the law that did this, the wave caused the incident. The wave was moved according to the law of physics, but not moved by them. However far you trace back, the law of nature never causes anything.. "

In nature we see the effect, but never the cause. As soon as we say "this is the cause", we immediately note that the cause itself is an effect created by another cause. So nature itself is only one huge effect. There must be and ultimate cause, and this cause must be God.

If nature was not ultimately caused by an intelligent Creator, then we cannot trust our own scientific thought processes.  For instance, if evolution is true, that is, if we came from a chain reaction of confusion into being, which being then evolved into us as we are today, then we actually originated from confusion.  Our thought processes are a part of what we really are.  If we have evolved from confusion and irrational causes, then our very thought has evolved from the same source.  If this is true then every particular thought of men is not intelligent, but comes from a flawed origin, and is intrinsically flawed itself.  If our intelligence is not trustworthy, then every theory that we advance is disproved as soon as we advance it.  We cannot trust our own power of reason if we have truly come from confusion, rather than from a Creator God.

(C. S. Lewis)  "I could not believe that 999 religions are completely wrong, and the remaining one true.  In reality Christianity is primarily the fulfillment of the Jewish religion, but also the fulfillment of what was vaguely hinted in all the religions at their best."

Another proof that God exists is the intuitive proof.  All men intuitively believe in a Creator.  Even the educated atheist believes in a god, though he will not admit to such a thing.  As the old saying goes, "There are no atheists in foxholes".  Death is the great equalizer.  If a devout atheist was to have his life threatened, his first instinct is to call on God.  After the high stress situation is passed the action is discounted as foolish by the same person, but there is no denying that the call was intuitively issued.  Men have always believed in a Creator, from the pagan to the Christian.  Lost tribes have been discovered that sacrifice to a Higher Being.  The rich call on a god when they are in danger.  The poor cling to God as their only hope.  All men everywhere have, at some point in their lives, known that there is a Creator.  Is this so strange?  As a hand crafter will leave his mark on the cabinet he has built, and as an artist will sign his painting, so God signed all that He created.  The signature of God on all mankind is that universal knowledge that He does exist.

Yet another proof of God exists in the conscience of men.  Humanity itself has a sense of morality and order that only could have been given to us by God.  How do we know what is the decent thing to do, except that it has been ingrained into us by our Creator?  If you ask any rational man "Is murder wrong or right", you know what answer you will get.  The adulterer feels a sense of guilt for what he has done because of his conscience. You can not say that we have this moral code just because it has been handed down by our parents.  Here we go back to cause and effect.  If morality has been handed down, then who started the system?  Who got the ball rolling so well that morality is accepted as an unspoken universal standard among men?  If mankind had said, "You know, it would be nice if we were moral", then how did we know how to define "moral" except that we had an ingrained sense of it in the first place?

What makes right "right" and wrong "wrong"?  Who set the standard?  If at some point someone just arbitrarily said, "It is wrong to murder", then what makes this position right?  If a Higher Being did not instill that moral code, then murder could be just as well right as wrong.  Maybe adultery isn't wrong after all, but just some man's idea of wrong.  Maybe the adulterer is right after all, as is the thief; or maybe God instilled the conscience with its moral code, and our perception of good and evil is correct.

Though nature has many proofs of God (as you have just seen), the character of God is never defined in nature.  When God created the earth His last creation was man, and He placed man in charge over all nature (see Genesis 2.15; 1.28-29; 2.19-20). When man fell through negative volition from the will of God, nature, as man's servant, fell with him (Genesis 3.17-19). Nature was corrupted, just as man was corrupted by the entrance of sin into the world. So though nature still carries the bold signature of God, it cannot define His nature for us. But we are not at a loss. God gave us a general revelation of Himself through nature, and a special revelation of Himself through the Holy Bible.

What are the characteristics of this special revelation of God, the Bible?  The Bible supplies reachable answers to man's problems.  It also rationally describes the nature of God to men.  Finally, the Bible explains the justice and mercy of God, harmonizing these two attributes.

The Bible claims to have a necessary knowledge of God:

Hebrews 1:1  "God, who at sundry times (POLUMEROS, in different portions) and in divers manners (POLUTROPOS, many different ways) spake (LALEO, Aorist Active Participle, communicated) in time past unto the fathers (Refers to the Old Testament Patriarchs)
 by the prophets (EN + Instrumental, By means of the prophets. Also see Psalm 109) , "

The Bible also describes the necessary knowledge of what God expects of men:

2 Corinthians 5:20-21 "Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God. For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him. "

Romans 3:21-23 "But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe (PISTEUONTAS, Present Participle, Linear Action, "Who keep on believing"): for there is no difference: For all have sinned, and come short of the glory of God; "

Though the Bible contains necessary knowledge of God, how can we know that the Scripture is the true special revelation?
 

(Watson) "No one has ever discovered the words that Jesus ought to have said .... no action of His shocked our moral sense .... some have puzzled us .... none have fallen short of the ideal ... He is full of surprises, but they were always surprises of perfection."

When we look at the prophetic witness of the Bible, the first place we must turn to is the life of Christ.  There were around 61 major prophecies concerning the coming of the Messiah, Christ fulfilling them all.  All of the prophecies concerning Christ were written before 450 B.C. Within the 61 prophecies there were 270 implications of detail.  The fact that Christ fulfilled all 61 of these prophecies proves two things: that He was and is Messiah, and that the Bible must be the prophetic Word of God to men.

In order to show you how complex this is, the following list gives the 61 major prophecies of Christ by reference only, with their recorded fulfillment in Christ:
 
 

According to H. Harold Hartzler of the American Scientific Affiliation, the chances of any one man fulfilling just eight of these prophecies in his lifetime is 1 in 100, 000, 000, 000, 000, 000. He illustrates this improbability by stating: "Suppose we take 100, 000, 000, 000, 000, 000 silver dollars, and lay them on the face of Texas.  This will cover the entirety of Texas to a depth of two feet.  Now take one of the silver dollars, mark it, and stir the whole mass thoroughly over the entire state.  Blindfold a man and tell him that he can travel as far as he wishes, but he must pick up the silver dollar and say 'this is the right one'.  What chance does he have of getting the right one?  Just the same chance that the prophets would have had of writing just eight prophecies and having them all come true in any one man."  All 61 major Old Testament prophecies for Christ came true in His lifetime.  Thus Jesus Christ is verified by the Scripture, and the Scripture by Christ.

There are other internal and external proofs that the Scripture is God's Divine Revelation to man.  The Prophecy of Ezekiel chapters 25-26 were all fulfilled in less than 20 years after its writing.  The Prophecy of Daniel 2.7-8 was fulfilled less than 100 years after its writing.  There is no way that the prophecies of Scripture could have been fulfilled so literally and completely, except that they came by the control of God.  We can with assurance trust what the Bible tells us of God and His nature.  It stands as the revealed word of God.