Probably for the existence of God. God's existence, if He were to have a reasonable fraction of the attributes ascribed to him, would be trivially provable to

Probably for the existence of God. God's existence, if He were to have a reasonable fraction of the attributes ascribed to him, would be trivially provable to the most hardened atheist. The fact that that hasn't happened, with no clear reason why not, is quite tricky for a lot of sceptics to get passed.