One can no more prove that God does or does not exist than he would try to measure "three feet of love" or "two pounds of justice."   Proving the existence of God is similar to proving the existence of George Washington or Napoleon.  We can no more "prove" that George Washington (or any other historical figure) existed than we can prove the existence of God.  The preponderance of evidence supports the existence of the father of our country, and that is all the proof we need.  There is a cute story which illustrates this:

      A college professor once was waxing eloquent to his students.  In his lecture he set out to prove once and for all that God did not exist.  He questioned his students dramatically, “Has anyone ever seen God?  Has anyone ever touched God?  Has anyone ever smelled God?  Has anyone ever tasted God?”  There was silence in the room.  The professor went on, “I conclude then, if He can not be seen, touched, smelled or tasted, that God does not exist.” 
      When the professor invited a response to his infallible logic, a student took the challenge.  He stood and asked, “Has anyone ever seen the professors brain?  Has anyone ever touched his brain?  Has anyone ever smelled or tasted his brain?  I conclude then, that our professor has no brain!”

      In the professor’s case, we might X-ray his head and present evidence that, yes indeed he has a brain.  We might also point out that he can reason, add, subtract, go grocery shopping and carry on an intelligent conversation.  And one day, when the professor has passed into the hands of God, science might take up the scalpel, remove his brain and place it on display as proof… but by then, what good would it do.   For at that point the professor would not be able to use his brain.  These are good evidences that the professor had a brain.  There are also good evidences that God exists.  Another story illustrates this point.

      Once upon a time two explorers came upon a clearing in the jungle.  In the clearing many flowers were growing.  One explorer says, “Some Gardner must tend this plot.” 
      The other disagrees, “There is no gardener.”  So they pitch their tents and set a watch.  No gardener is ever seen.
      “But perhaps he is an invisible gardener.”  So they set up a barbed wire fence.  They electrify it.  They patrol with bloodhounds.  But no shrieks ever suggest that some intruder has received a shock.  No movements of the wire ever betray an invisible climber.  The bloodhounds never give cry.  Yet the believer is not convinced.
      “But there is a gardener, invisible, insensible to electric shocks, a gardener who comes secretly to look after the garden which he loves.”
      At last the skeptic despairs, “But what remains of your original assertion?  Just how does what you call an invisible, intangible, eternally elusive gardener differ from an imaginary gardener or even from no gardener at all?”

      This parable is a damning judgment on all religious claims… unless the Gardener should happen to be seen caring for his garden!  How do we know that God is real?  We always come back to the main thing:  Jesus Christ invaded planet earth.  He claimed to be the Gardener - God himself.  He died and rose from the dead.  His followers unwaveringly testified to this fact.  His claims and his resurrection are one of the main evidences that God exists.  The best and clearest answer to how we know there is a God is that He has visited us. 

      2000 years ago, Jesus entered the human race in a small Jewish community.  He was a member of a poor family, a minority group, and resided in one of the smallest countries in the world.  He lived only 33 years and his public ministry only lasted a short three years, yet people everywhere still remember him.  The date of our morning newspaper bears witness to the fact that Jesus lived the greatest of lives ever.  Jesus is the most influential life ever lived on this planet.  Examine the life and claims of Jesus Christ.  Jesus claimed to be God.  He didn’t leave any other option open.  His claim must either be true or false… it must be given the most serious consideration for on it hangs eternity in the balance.