What are the alternatives to explaining everything about the brain? As far as i can tell the possibilities are that it is equivalent to a 1. computation that

What are the alternatives to explaining everything about the brain? As far as i can tell the possibilities are that it is equivalent to a 1. computation that can be performed on reasonably sized Turing Machine 2. computation that requires too large Turing machine, (in which case we still most likely can build an alternative implementation of a brain using some other physical phenomena) 3. the function that appears to be performed by brain is not performed by brain, so we do not have a way to recreate that function by studying the brain. Whichever of these you assume to be true, the job of the scientist remains the same: poke at the problem until you build a good model of the brain and see if it works or not. And since there is no difference, and there is a huge amount of indirect evidence for the first hypothesis there's nothing wrong with using it as the main working hypothesis.