I'd be very interested in knowing what this "sense" is -- I don't think there is one. I chose waterfall by symmetry with a hydraulic computer. A waterfall is j

I'd be very interested in knowing what this "sense" is -- I don't think there is one. I chose waterfall by symmetry with a hydraulic computer. A waterfall is just what we call a hydraulic computer when we're not using it for computation. I still only see an observer-relative distinction (ie., in how it is used). One can "juggle rocks" to compute. You've said something about "inputs" and "useless when removed". Both of these are again observer-relative. Useless gives it away. An animal isn't "useless" when its brain is removed, because it isn't our use of it which makes it alive.