The sensory side of the nervous system is disturbing in that it creates a reality for the individual which is not the same as the true reality. For example, when there is a lesion in the parietal lobe (which is known to occur in patients suffering from a tumor, stroke or other cerebral vascular accident) they experience hemineglect in that they will not and cannot admit to having a side of their body, normally the left side. In this case the patient will comb their hair on one side of their head, apply lipstick to only half of their lips, etc. Clearly their perception of themselves is not accurate in the sense of onlooker's reality. Similarly, every human can only detect certain frequencies of sound, light etc. Just because we can only detect the certain frequencies, commonly we believe that these are the only frequencies that exist. But with the aid of technology we can detect things that before did not exist for us. In this sense we are uncovering the true reality of our environment. On the other hand, we can never know the precise true reality of the environment because there could be a different thing similar to light or sound but different in that we have no perception of any of its frequencies. Therefore, we can never uncover this portion of reality as we have no perception or awareness of any sort of its existance. Thus, we can be sure to never know what true reality is. This is especially disturbing because it means that the brain is responsible for creating what an individual thinks is reality although it is not an accurate reality.
Alternatively, one might think of it as exciting, enfranchising? Along this line "true reality" might be thought of as an idea created by the nervous system rather than something definite out there. And then what one has to do is not to worry about whether what one sees is "true reality", but rather to enjoy finding new things that one didn't know about before. Even without a "true reality" one can happily go about creating a better and better one, no? PG