There is an interesting passage of scripture in Romans 1. It's the introduction to this book of grace as Paul unpacks our sin problem and God's wonderful grace as its remedy. In Romans 1 are these words, "...that which is known about God is evident within them; for God made it evident to them." From these introductory words Paul tells how man, in spite of knowing that God exists, has denied him and exchanged his worship for lesser things, his glory for their own, his ways for the ways of men. But, before you can reject God completely you have to somehow convince yourself that he's not really there.....knowing the whole time he really is.
What the bible declares here and in other places is this- there are no true atheists, but only men and women who deny what they know, deny what God has made evident to them already. Everyone knows there is a God and we are accountable to him, but many simply turn their backs and walk away. As one atheist said, "I don't want there to be a god...." and so they dismiss the God who is from their lives and actions.
But, there are consequences for that choice. From that first choice of rejection comes a downward spiral of confusion and poor choices, not clarity and better choices. The one who rejects God doesn't demonstrate greater insight, but less. He has chosen to dull his mind to the core of knowing anything and the result is that everything else is duller, dimmer, fuzzier. Thinking is clouded and choices become confusing.
Job the man of great trial in the Old Testament, made a statement that unpacks this better than I could as he wrote in Job 28:28,
"And to man He said, 'Behold, the fear of the Lord, that is wisdom; And to depart from evil is understanding.'"
So, how do we respond to the embedded knowlege that God exists? The first choice and best by far is to acknowledge him as God and worship him for who he is and what he has done. It is the honest admission that we aren't as smart as we think we are. It is the honest declaration that we are created beings subject to a creator, but it is the starting place for finding true wisdom.