"[I] think of the concepts as the address space for our behavior programs. The behavior programs allow us to recognize objects [also mental objects] and react... [A] large part of that is the physical world that we interact with, which is this ' thing... basically the navigation of information in space... [I]t's similar to a ... a physics engine that you can use to describe/predict how things that look in a particular way, that feel... a particular way, enough , enough auditory perception... the geometry of all these things... [T]his is probably 80% of what our brain is doing... dealing with that... real time simulation... [I]t's not that hard to understand... [O]ur game engines are already approximating the fidelity of what we can perceive... in the same ball park... just a couple of orders of magnitude away from saturating our perception, from the complexity that [the brain] can produce. ...[T]he computer that you can buy... is able to give a perceptual reality that has the detail that is already in the same ball park as what your brain can process."