But we don't understand the high-level 'physical rules' of the brain. While gravity could be explained by simple equations, the high-level operation of the brai

But we don't understand the high-level 'physical rules' of the brain. While gravity could be explained by simple equations, the high-level operation of the brain has escaped us despite a lot of effort. This goes back to the top-down vs bottom-up debate in studying the brain. What you are discussing is a top-down approach, where we understand what the brain does and then figure out how it works from there. A lot of people believe the 'correct' path is more similar to a bottom-up approach, where we understand the lowest levels of the brain and work up from there. This may be more feasible because we may actually have a chance at comprehending what a single neuron does. But amazingly our understanding of a single neuron's behavior is still limited. Some scientists believe we would need an entire computer to properly simulate what a neuron does (and others believe a standard computer can't physically do it). There's a third group of very pragmatic people who believe the best approach will be a compromise between top-down and bottom-up - meaning we may not need to perfectly simulate a neuron nor completely emulate the brain's higher level function to make progress in understanding how the brain works.