All the debates, arguments, and theories are for people who either don't know or who 'believe'.
For example I don't 'believe' in God, I know with absolute certainty of His existence. At one time I simply 'believed' in Him but when He showed up and saved me 20 years ago, all doubt was erased.
The interesting thing is? I am unable to convince another by any means that this is true. Therefore, I have become convinced that absolute certainty of God's existence is something that God Himself must undertake with the individual.