Again, unless you are a dualist, we can put comfortable bounds on what the brain is. We know it's made from neurons linked together. We know it uses mediators and signals. We know it converts inputs to outputs. We know it can only be using deterministic and random processes.

We don't know the architecture or algorithms, but we know it abides by physics and through that know it also abides by computational theory.

https://www.dictionary.com/browse/duelist