You can know OF god, but you can not possibly know all of god.
If you think that you definitely know god, that's only the god of this world that you know…
Imagine demanding that the world make sense to you.
You can't even know the totality of the principles which govern things though. Attempts to do just that are exactly why some people believe this world is governed by dark powers; They expect they can know such things, so when they invariably learn that they never did, they perceive it as some malevolent force fucking with them.