I think you're confusing things here. The reason why MS is conceived of as a disease is because it contradicts our notions of what the human organism should be like. If we conceptualized MS as being some kind of mark of divine attention (or whatnot) it would not be considered a disease or an object of medicine. Psychotic delusions are analogous, since there is no way of knowing that we ourselves are not deluded in our appraisal of the other as being deluded. It's not like we would know.
----- Original Message ---- From: Vincent Clarke <pclarkepvincent at gmail.com>
You see it's not a logical or even a philosophical problem; it's a medical problem. I'll give an analogous problem from the sphere of neurology. Say a neurologist comes across an MRI scan where someone is showing the first signs of Multiple-Scerosis. Now, the neurologist has to make a call: is this MS or is it not (it could be ADEM, for instance, or one of the other "Borderline MS" diseases) - the neurologist also has to make a call in relation to prescribing medication, which is a pretty big call. So, there's no concrete basis for judging the condition. This is because its a nosological rather than a logical judgement, based on experience and intuition rather than on pure logic - but it has major practical consequences.