Here's the wiki definition: So, for example, "Visual processing is the sequence of steps that information takes as it flows from visual sensors to cognitive processing. The sensors may be zoological eyes or they may be cameras or sensor arrays that sense various portions of the electromagnetic spectrum." Re: nerves, here is a description (from http://www.apparelyzed.com/spinalcord.html) "The anatomy of the spinal cord itself, consists of millions of nerve fibres which transmit electrical information to and from the limbs, trunk and organs of the body, back to and from the brain. The nerves which exit the spinal cord in the upper section, the neck, control breathing and the arms. The nerves which exit the spinal cord in the mid and lower section of the back, control the trunk and legs, as well as bladder, bowel and sexual function. The nerves which carry information from the brain to muscles are called motor neurones. The nerves which carry information from the body back to the brain are called sensory neurones. Sensory neurones carry information to the brain about skin temperature, touch, pain and joint position." Does that give you an idea of what I'm getting at? From wiki: Equations, as I see them, are attempts to describe certain observed properties of matter. They are attempts to describe past observed patterns in a way that predicts future patterns. Just as words cannot provide complete descriptions of the things they describe, neither can equations. There's no reason to assume that every aspect of reality is conducive to description through equation. To expect otherwise is to have unrealistic expectations.