Who has seen the wind?
Neither I nor you:
But when the leaves hang trembling
The wind is passing thro'
Who has seen the wind?
Neither you nor I:
But when the trees bow down their heads
The wind is passing by. - Christina Georgina Rossetti
The wind blows where it wants to, and you hear its sound, but don't know where it comes from and where it is going. So is everyone who is born of the Spirit. (John 3:8)
There are ideas of which the truth of them cannot easily be fully understood or satisfactorily be proven logically without the element of faith – the existence of God is but one of them.
Consider the whole concept of the entire universe. With all of man's sciences, can he fully fathom the vastness of the expanse of the universe and the ever growing number of cosmic bodies with the countless molecules of all the matters that comprise them, and explain completely how everything works as they are in perfect order and harmony? Not, of course. This fact just demonstrates the finiteness of the capacity of the human understanding. If to completely comprehend the fullness of the physical realm (the entire universe) is beyond the capacity of mankind, how much more far beyond mankind's capacity is it to completely comprehend the fullness of the metaphysical realm?
God, a metaphysical entity, cannot be proven adequately using concrete physical methodologies of science. The acceptance of the truth of God is primarily a function of faith rather than of reason. To attempt to explain the fullness of God using the finite human understanding defies basic principles of logic. It would be comparable to an ant trying to fully understand a computer with all of its complexities.
As beauty is in the eyes of the beholder, faith is in the inner being of the believer. How else is beauty perceived but by the "seeing" of the object of beauty? ("Seeing", as used here, does not refer only to the perception through the faculty of the eyes.)
Similarly, faith comes by "hearing" the truth of God. ("Hearing", as used here, is not limited only to the perception through the faculty of the ears.)
Faith is the substance of things hoped for; the evidence of things not seen.
You know that another human being is in the other end of the phone because he/she hears and understands and responds consistently according to what you are communicating. Answered prayers of true believers are not just one manifestation of the existence of God, but also it is an evidence that God is a living metaphysical entity with an intellect that is far beyond man's. God hears and responds accordingly as asked but in ways not always understood. non-existent, or non-living, or imagined beings do not hear nor respond.
Do you want to prove yourself that God really exists? Do you have any real problem that is beyond your immediate capacity to solve? Try asking God for help by praying a “valid” prayer. When your prayer is answered, you will perhaps begin to believe. To see is to believe? Try again every next time you have a bigger problem.
To discover that “God is who God is” can only be possible by faith. To believe is to see.
Blessed are they that have not seen, and yet have believed. (John 20:29)