We have all experienced it: that moment when Satan whispers in your ear, "You aren't really a true Christian or you wouldn't think or behave like that." It is one of our enemy's most effective tactics to spread uncertainty and render God's people ineffective with self-doubt. But how do we know we are a Christian? Roberts writes, "to be in a gracious state is true happiness. But to know ourselves to be in such a state is true happiness doubled...