Yes there is no clear place to draw the line between faith and reason. That’s why we need to trust in God to guide us.
You might as well substitue ``astrology'' or ``Satan'' or ``Flying Spaghetti Monster'' for ``God'' here. There is no real value in this statement, other than what it means to you. The problem is that ``God'' is a question of faith, and faith is dependant on culture. Asking someone who was raised in Saudi Arabia, who is a good and loving Muslim, who gives money to orphans and loves his wife, and whe fears and loves Allah to accept Christ is unreasonable.
Your answer will be ``If God calls him then it is up to him to answer'', but this is not an objective statement. If the man is a muslim, and dies a muslim, then he didn't heed God's call. I know this paradigm well---if someone falls on misfortune, then it is because they turned away from God, and not some string of coincidental events that conspired against them. If the Canaanites were masacred (killed by the edge of the sword = hacked to pieces---check the old testament) by the Jews, then it is because they didn't trust in God. If the Israelites killed women and childeren, and animals along with the men, it is because the Canaanites were standing in the way of God's will.
If you read the Old Testament literally, and believe that God gave the land of Canaan to the Jews, and that the Jews were doing God's will as they slashes Canaanite women and childeren to pieces, then you call Islam a violent religion, then you are a hypocrite.
The problem with ``God's will'' is that it is a highly subjective thing. If I think that it is ok to drink alcohol, and you do not, then it is I who am disregarding God's will. If I want to marry another man, in the church, and you think that it is an aberration of nature, then it is I who am turning against God's will.
We are each in the unique position that God has told us what he wants us to do. And if what God has told me conflicts with what God has told you, then YOU are wrong, and not me. It is YOU who are disregarding God's will.