This kind of question dates back to the beginning of the branching off of Christian religions, such as Calvinism, Puritanism, and Antinomianism. John Calvin believed that his god was omniscient and omnipotent, so it was in his power to know and control who would get into heaven and who...
Since you and I both have all the resources in the world that give us the ability to discover our existence/nonexistence, and you aren't able to discover whether you exist or not, how should I know if I exist or not? Furthermore, if I don't know if I exist, why should I have the ability to know...