So, / I'm gonna use / a metaphor to describe how the brain / works. / It goes something like this: / Your brain, / my brain, / everybody's brain, / is trapped / in its own / dark, / silent box / called / your skull. / And / the brain / has no knowledge / of what is going on / around it in the world / or in the body, / right? / Because it's in this skull, / and it's receiving sensory signals / from the sensory surfaces / of your body. / These signals / are the outcomes / of some changes / in the world / or in the body / — but the brain doesn't know / what the changes are, // it's receiving the outcomes. / And that / is what / philosophers and scientists call / the 'Reverse inference problem.' / You start with an outcome, / and you have to guess / at the cause. // For example, / if you hear a loud bang, / it could be / a car backfiring, / a door slamming, / it could be a gunshot. / Your brain doesn't know / what the causes are, / it only knows the effect, / and so, / it has to guess. / And the guess is important, / right? / Because you would do different things if it's a gunshot versus if it's a / windy day that slammed a door. / And luckily, / it has one other source of information, / and that is your past experience. // The really cool thing about this /—if that wasn't cool enough / —is that it's actually doing it predictively. / Sometimes scientists talk about this as the brain running a model of the world, / but the brain is not running a model of the world; / the brain is running a model of its body, / and it's doing it in this really interesting way.