#19 If you cannot be sure, it means that you may be wrong, and if you may be wrong it logically follows that you do not know.
If you do not know that you are experiencing the real world, and not a projection, then you cannot know anything, not even math.
"but you can never be sure you understand the true nature of things." <Are you sure what you wrote and How do you know? Is it true what you wrote or could you be wrong?
What must exist before for all things to make sense? What must exist before providing the basis for relying on the validity of your senses, laws of logic and reasoning to know that the world around you is real and not a simulation?
R: God and God's revelation to his creatures about the nature of reality
The Bible says that everyone knows that God exists, and that is why everyone knows that the reality in which they live is real, not a matrix or illusion. You know that math is real, because first you know that God exists