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>PI § 246In what sense are my sensations private? -- Well, only I can know whether I am really in pain; another person can only surmise it. -- In one way this is wrong, and in another nonsense. If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain. -- Yes, but all the same not with the certainty with which I know it myself! -- It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean -- except perhaps that I am in pain?
Other people cannot be said to learn of my sensations only from my behavior -- for I cannot be said to learn of them. I have them.
The truth is: it makes sense to say about other people that they doubt whether I am in pain; but not to say it about myself."
http://www.dolosys.de/index-EN.htm>The Paintracker is a handy monitoring device to determine the analgesic depth needed for patients based on the pain reflex technique. The effects of pain therapy can therefore be measured using an objective parameter and concrete treatment recommendations can be derived from these measurements. 
