Share 'Athiests'

What is the best way to witness to a self-proclaimed athiest? He appears to want to tie my hands and wants scientific evidence when quoting scripture. I realize that some people just want to play games, but he keeps coming back and I don't want to ignore him. There has to be a reason why someone like this spends so much time and effort on something he professes not to believe in? Of course, not b…