Scripture does not attempt to prove the existence of God; it
asserts, assumes, and declares that the knowledge of God is universal,
Rom. 1:19-21, 28, 33; 2:15.
It asserts that God has wrought this great truth in the very warp and
woof of every man's being, so that nowhere is He without this witness.
The preacher may, therefore, safely follow the example of the Scripture
in assuming that there is a God. Indeed he must unhesitatingly and
explicitly assert it as the Scripture does, believing that "His eternal
power and divinity" are things that are clearly seen and perceived
through the evidences of His handiwork which abound on every hand.
Even God Himself is satisfied with the evidence of His own existence. He requires no further proof.
he left not himself without witness, in that he did good, and gave us
rain from heaven, and fruitful seasons, filling our hearts with food and
Acts 17:23-29...For as I passed by, and
beheld your devotions, I found an altar with this inscription, TO THE
UNKNOWN GOD. Whom therefore ye ignorantly worship, him declare I unto
you.  God that made the world and all things therein, seeing that he
is Lord of heaven and earth, dwelleth not in temples made with hands;
 Neither is worshipped with men's hands, as though he needed any
thing, seeing he giveth to all life, and breath, and all things; 
And hath made of one blood all nations of men for to dwell on all the
face of the earth, and hath determined the times before appointed, and
the bounds of their habitation;  That they should seek the Lord, if
haply they might feel after him, and find him, though he be not far from
every one of us:  For in him we live, and move, and have our being;
as certain also of your own poets have said, For we are also his
offspring.  Forasmuch then as we are the offspring of God, we ought
not to think that the Godhead is like unto gold, or silver, or stone,
graven by art and man's device.
Romans 1:18-20...For the wrath of God is
revealed from heaven against all ungodliness and unrighteousness of men,
who hold the truth in unrighteousness;  Because that which may be
known of God is manifest in them; for God hath shewed it unto them. 
For the invisible things of him from the creation of the world are
clearly seen, being understood by the things that are made, even his
eternal power and Godhead; so that they are without excuse:
The Bible automatically assumes the existence of God. The Bible
automatically assumes that all of mankind knows of the existence of
God. And that denying such existence is profoundly disproportionate
making sin a distortion of the human mind.
even as they did not like to retain God in their knowledge, God gave
them over to a reprobate mind, to do those things which are not