1. “It says in the Bible…” Don’t start out conversations with this. Why imply he should believe a book written by someone who, in his terms, doesn’t exist?
2. “Science (or evidence) says…” Science can’t speak (neither can evolution, come to think of it); this is the fallacious mistake of reification, or, turning some abstract concept into something that is physical or alive. If you need help understanding this fallacy, read the Wikipedia article here.
3. “If you don’t believe in Jesus Christ (or God) you will go to hell.” While this is true, jumping right to the point without making him see his need will only create tension. Same as with #1, you can’t start right out with the Bible because he has rejected it.
4. “Where do you get your values?” (or) “How do you know right and wrong?” While it seems logical for us, the Christian, to believe right and wrong have to come from some set Person or Thing, the accepted belief is that right and wrong are cultural, social, or relative norms. Most people lean towards the postmodern belief that everyone makes up their own right and wrong.
If you mean this question as an argument to eventually lead back to a “divine foot in the door,” you might find yourself in a new maze of postmodern or relativist arguments (such as “Everyone lives in their own separate reality” or “That’s just your truth…”).
More to come.
In #3, I believe you’re trying to avoid the gospel. You realized that “it’s truth” when you say the phrase “You will go to hell.” We can’t know for sure who is elect and who isn’t, who is saved and who isn’t, but maybe that atheist isn’t elect. That’s why God has lead that person down the road of atheists. That makes you wrong, because you commit the fallacy of assumption. I don’t witness to people who aren’t Christians because I can’t know if they are elect. The job of saving and election is entirely up to God.
Let me narrate your objection: Firstly, you say I’m avoiding the gospel by avoiding the truth of telling people bluntly that they will go to hell without Jesus. Secondly, you tell me that we cannot know who God has elected for salvation. Then you tell me implicitly I should not witness to people who are not Christians. You finish with an entirely different objection, and I quote: “The job of saving and election is entirely up to God.”
If you accuse me of avoiding the sharing of the gospel and accuse me of sharing the gospel, what am I supposed to do?
Personally, I’m both Calvinist and freewill, see http://echoesinthewind.wordpress.com/2010/11/26/what-is-predestination/.
If you have the time, browse http://echoesinthewind.wordpress.com/2011/10/06/double-standard-facts-and-values-feel-free-to-add/ and see for yourself how atheists think. Some of these are top atheist bloggers.
You are supposed to pray for atheists and have faith that they will come to a saving knowledge of Christ!