Why isn't God's existence obvious to everyone?

If God is so all-powerful, why can't we prove that he exists?
 
I believe that God exists, that He brought the universe into being, that God the Son redeemed us through his death, and was resurrected as a token of God's power, that God the Son sustains the created universe at present, and that God the Holy Spirit guides believers now. I also believe that the claims in the previous sentence cannot be unquestionably proved, mathematically, scientifically, or logically. As the scripture quoted in the graphic at the top of this post puts it, "By faith we understand that the universe has been framed by the word of God, so that what was seen has not been made out of things which are visible." (Hebrews 11:3)

The author of Hebrews does not explicitly say that we can't unequivocally prove the existence of God to doubters, but it implies that, and common experience indicates strongly that we cannot prove God's existence irrefutably to a doubter.

Why is this so? Why does God hide himself? One classic answer is that, in this way, God allows for choice to believe as part of the free will of human beings. If God's existence were that obvious, everyone would be a believer.

Recently, Jim Stump, of the BioLogos Forum has posted on this question. I'll let you read his post, but will say that Stump believes that God has arranged things so that He is hidden for another reason, which Stump spells out. (Stump's post is partly based on a book by John Mullen, and Stump also refers to his own previous posts on the subject at hand.)

See also my post on Hebrews 11:3, Read Stump. Thanks for reading this.