Real world systems are complicated. In theory, you could do belief propagation to update your beliefs through the whole network, if your brain worked something like a Bayesian network.
Natural selection didn't wire our brains to work like a Bayesian network. If it had, wouldn't it be easier to make converts to the Church of Reverend Bayes? /s
Alternatively, brains ARE Bayesian networks with hard coded priors that cannot be changed without CRISPR.
