The first challenge was to understand perception as an active, action-oriented construction, rather than as a passive registration of an objective external reality. Our perceived worlds are both less than and more than whatever this objective external reality might be. Our brains create our worlds through processes of Bayesian best guessing in which sensory signals serve primarily to rein in our continually evolving perceptual hypotheses. We live within a controlled hallucination which evolution has designed not for accuracy but for utility.
