One can for instance predict the weather without simulating the path of every molecule and atom in our atmosphere ... The human brain can be simulated in similar detail.
Ah, so it can be simulated to a rough degree of accuracy, but no better? And you can guess what it will do some of the time, and other times it will behave totally freakishly and unpredictably?
Not a human being I'd want to hang around with. Keep it away from sharp implements.