A -> B -> A -> B -> A -> A

You: "But what if our brain is limited by the simply fact that it's a limited material inside the universe we live in?"

Him: "Regardless of the mind body problem, even going by the matrealism, anything that isn't everything(anything, basically) in reality is an outdoor expression of reality's deepest essense, where everything is one and the same. And since our limited brain can understand reasons of stuff to some extent, why wouldn't he be able to understand reality's deepest essense?"

You: "Since when does reality has a thought structure? Maybe some of reality's "rules" are random?"

Him: "Randomness is also a reason."

You: "But we can't understand randomness as a reason! Anytime scientists don't find a connection between A and B, they assume they haven't found the right connection! We can't recognize randomness! It's the opposite of reason!"

Him: "Godammit.."

You won.