We can then imagine that this same friend's nervous system might be manipulated (whether through mutation, injury, or pharmacological manipulation) to prevent them from feeling pain. While we might initially be shocked at such a turn of events, we could be convinced of such a change if our friend stopped responding to usually painful stimuli (such as our villain the stove-top) with the same clear "pained" reaction. So changing the nervous system clearly changes whether or not the individual can feel pain, leading us to believe that pain is something the brain does.
|Pain is something the brain does- but how do we know when it is doing it? Image from here.|