It's good to witness to someone. James 5:20says,Whoever turns a sinner from the error of their way will save them from death and cover over a multitude of sins.I remember hearing a young man who was rather skilled at street evangelism sharing with another young man, an electrician, after a ball game. Toward the beginning of the conversation, the electrician asked How do I know your God is the real god, and not Odin or one of those other gods?A while later, I heard him say, Okay, I'll be honest. I know there is a God, and I know I'm not right with him.A lot of this junk people throw out there are just excuses. Romans 1tells us about men who do not like to retain God in their knowledge. The truth is there, and people build up a wall of beliefs and excuses to block their own view of the truth.It may help to treat him like he's in denial, that on some level he knows what the truth is. You can answer his objections and challenge his believers, but sometimes it may help if you are more concerned with telling him what he needs to hear than with addressing his objections. The word of God is powerful. Talking whatever philosophy he's dreamed up may not be that powerful