I once had a discussion with a self professed atheist and she basically questioned the existence of a God in a world where children are murdered, abused etc. and I prayed quietly on the spot asking God to answer her question and I opened my mouth and words just came pouring out about the concept of Omnipotence and a scenario where and Omnipotent being said something it had to happen by the nature of Omnipotence. Considering this concept if such a Being said that if someone sins then the out come is death, that this had to become fact. That such a Being made a child with free will and this child chose to sin and was condemned to death having done this act. What would such a being do, considering that this Being was the most perfect parent filled with the most perfect Love that would never die, how this Being would feel compelled to save the child from this most certain death, enter the plan of God through Jesus the Christ. She sat and reflected and was challenged to reach out to this "Hypothetical Being" for herself and she said she would as her stance had been shaken somewhat.
Now in all this it seems to me that she had reasoned her way into the position that she had taken based on what she felt was a solid argument and many of us being confronted with many "False Christians" or actions by christians that seem un-christian, added to the prevailing wickedness that seemingly goes unchecked, begin to argue themselves into positions where they begin to question the contents of the Bible or look at it as just stories meant to make a point on moral issues etc. and are afraid to believe to deeply and the only way to break through this is by the intervention of God as He knows the true reasons for our position and how to give us that break through that we need to make the right choice. SO a silent prayer in the midst of the discussion is an effective tool to assist someone in discovering the Truth about the Scriptures.