Is it up to the worshiper of God to prove anything to anyone else?

I've often wondered about this. It amazes me how two people can look at the same event and conclude two completely different opinions. One will be floored by the miracle and the other be completely unmoved. It makes no sense to me. From the Bible, I know Christ died for us all but realistically, I think some people are incapable or perhaps,so completely unwilling to see God everywhere...even when it's staring them in the face.