I recently had a colonoscopy under an anesthetic that caused complete amnesia. An observer could see I was in extreme pain during the procedure yet I have no recollection. How does a philosopher think about the pain I experienced but do not recall?

In my view, experienced pain still counts as pain, even if it is not later remembered. The key here is that the pain was actually at one time experienced.

Some kinds of anesthetics block pain experience altogether -- for example, when pregnant women have c-sections, they typically do not experience the pain while the procedure is going on and the anesthetic is in effect. (After the anesthetic wears off, well, that's another story altogether...)

In contrast, you describe a different kind of anesthetic, one that does not stop the pain from being experienced, but just stops it from being later remembered. And I would say that unremembered pain is still clearly pain. Here's one way to think about it. Suppose that right now, while fully conscious, you were offered a deal: If you agree right now to be tortured, you will get $10,000. You will be in extreme agony for an hour, but afterward, the torturer will give you a drug to make you forget the torture entirely (and you will get your $10K). Would you accept the deal? Insofar as we aren't inclined to go for it, it seems that we accept the claim that unremembered pain is still pain. (Test your intuitions further: Does it matter if the reward goes up to $1 million? Does it matter if the torture is extended to six hours? Or three weeks?)

That said, my understanding is that the anesthetics typically used during colonoscopies do not work entirely as you describe. Usually, I think, some Demerol (or other pain killer) is given, so there isn't experienced pain that is then forgotten but rather no real pain is experienced (perhaps there is some discomfort, but not pain).

if you have to have the procedure again, perhaps it would be smart to talk to your doctor to clarify the properties of the anesthetics being used. And in any case, I hope the results of your procedure were good ones.

Daniel Dennett discussed a fictional drug that he called an "amnestic" that allows you to feel pain, but paralyzes you so that you don't exhibit pain behavior, and leaves you with amnesia. Pleasant, no? For the details and his philosophical analysis, read:

Dennett, Daniel C. (1978), "Why You Can't Make a Computer that Feels Pain", Synthese 38(3) (July): 415-456; reprinted in his Brainstorms: Philosophical Essays on Mind and Psychology (Montgomery, VT: Bradford Books (now Cambridge, MA: MIT Press), 1978): 190-229.

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