I want to give examples of two different kinds of experiences that I will then try to classify in order to explain an idea.

On the one hand consider the following cases. Suppose you have a bug bite that itches, or suppose your back itches. You scratch the bug bite or get someone to scratch your back and it feels really good to do so, very satisfying, at least for the moment. Or suppose you have lost something important to you and you are all in distress about not being able to find it. If you do find it while frantically looking for it, it can not only make the tension go away immediately, but it can bring a rush of happiness and excitement, the relief will be so intense -- making you feel far better than if you had not even lost it in the first place. Or a sneeze might release the tension from some sort of tickle in your nose or sinuses. In all these cases the feeling of displeasure ends with some particular action or at some fairly well-defined time, and it ends in a way that is pleasurable. 

The initial feeling that ends in a rush of pleasure does not even have to be unpleasant or disagreeable. Anticipating receiving something may be a pleasurable kind of feeling but still be crowned by actually receiving it. Or one can have a taste or craving for some sort of food without being in any discomfort or "starving"; for example, one might see a particularly mouth-watering dessert and look forward to sampling it with pleasurable anticipation. Or sex, for example, may be very pleasurable prior to orgasm and yet an orgasm may still be a particularly pleasurable, climactic end to the urge to continue having sex for the moment. It is not necessarily an end to touching or snuggling, but it is typically at least a temporary ending to the "sexual" or "sexual desire" part of the moment. Even if someone is capable of multiple orgasms, such that the first or second orgasm does not quench their urge to continue, at some point usually there will be a definitive end.

On the other hand, contrast all those kinds of cases with ones where whatever resolves the discomfort or brings any desire or feeling to a close is something that is not particularly noticeable in its occurrence. In some cases we don't even have a word for it. For example, a headache normally just sort of disappears without its happening at some particularly climactic time. It is not like getting morphine for a wound or Novocain for an abscessed tooth causing extreme pain to disappear fairly suddenly. One might not even notice a headache is gone until one remembers having had one earlier. Realizing one's headache is gone may make one feel good, but it is not "climactic" in the way a sneeze relieves a nose tickle or a yawn relieves the feeling one needs to yawn. There is not usually some dramatic or climactic end to, or relief of, a headache. Or one might be worried about something and then get distracted in a way that makes one forget about the issue. Or one can be bored and then have something come to one's attention that one finds interesting enough to relieve the boredom, but not with any particular rush of excitement.

Good feelings themselves tend to sort of fade rather than ending abruptly (apart from the pain of a sudden injury or the sadness of hearing bad news, that replaces them). In Mansfield Park, Jane Austen says "It was long before Fanny could recover from the agitating happiness of such an hour as was formed by the last thirty minutes of expectation and the first of fruition."

In some cases, such as hunger or thirst, the initial feelings may be pleasant or unpleasant. One can be so hungry or thirsty that one is suffering, or one can just have a feeling of anticipation for some particular food or beverage.

And, of course, there are things that feel good for which there might not have been some feeling of "need" or some "urge" that required satisfaction. One might not be hungry and yet be given a kind of food for the first time which causes a rush of pleasure at the taste. Or one's back does not have to itch or have sore or tense muscles in order to have a back scratch or a back rub feel good. They feel good without some prior sensation of discomfort, frustration, anticipation, or desire. But I am interested in the cases where there is some sort of initial feelings, whether of discomfort, anticipation, desire, urge, agitation, frustration, etc. rather than in cases of totally unexpected pleasures. For short, I will simply call these initial feelings the "itch", but I am using that only in the sense of desire, as in "I am itching to get out of here" or "I am itching to get my hands on a Corvette" (or "some Boston cream pie") or "I am itching to find out how this book ends", etc.. 

With all this as prelude, the distinction I am trying to make is between those feelings which come to a sudden kind of "conclusion", typically in a noticeable feeling of pleasure or excitement, and those which more or less fade out or disappear over time, without any particular sense of resolution, satisfaction, or fulfillment. In the latter case, it is not usually that the itch is scratched, in a metaphorical sense, but that the itch simply disappears. The initial feelings are not fulfilled or assuaged in some way but, if they go away at all, they simply fade out or end. In the case of an itching bug bite, for example, there is a difference between the way it feels to scratch the itch and the way it feels to have the bite stop itching an hour after you have applied something like a cortisone cream. It feels really good to scratch the bite, but it does not feel really good simply to have stopped itching, even though one might be very grateful and appreciative of its having stopped itching. Even when scratching does not stop the itching (or even when it makes the bite itch more) there is something really pleasurable and satisfying about scratching that is very different from having the itch simply go away.

Or consider a yawn that is satisfying and one that is not -- one that doesn't quite give you that "release" of whatever it is that is making you yawn. There is a trick you can even do to people who are starting a yawn: put your index finger as though you are about to put it in their mouth as it opens for the yawn. They will reflexively close their mouth and that will stifle their yawn very effectively, but not pleasurably or satisfyingly for them at all. They will no longer feel like yawning, but they will not feel good about it either.

Thus, it seems to me to be reasonable to ask why some itches have scratches and why some do not. And it seems to me that since not all itches have scratches, and that many of those which do, do not really need them, that itches which have concomitant scratches -- climactic or relatively immediately resolved endings -- do so either by accident, coincidence, or chance, or that there is an accidental mechanism which somehow causally gives rise to the itch and the scratch at the same time in some way. 

Moreover, and perhaps more importantly, it seems to me there is reason to believe we can have itches that neither go away on their own nor have any sort of scratch or resolution. I am not meaning that we have itches that we cannot "reach" in some way, as with a leg that itches in an unreachable place in a cast or a bug bite in the center of one's back when there is no implement to scratch with or nothing to scratch against. I mean it might be that something like "anxiety" is an itch without a scratch, or that paranoia is an itch without a scratch. Jumpiness or nervousness or the inability to relax ("ants in one's pants") might be itches without scratches. Materialism or consumerism may be an itch without a scratch. Envy and jealousy may be itches without scratches. Wanderlust may be an itch without a scratch. The desires to find eternal love or to find goodness or beauty may be itches that have only limited numbers of scratches, if any. Boredom may be an itch with only an occasional scratch. Lethargy may be an itch without a scratch. The search for knowledge and/or understanding may be itches without scratches, or with only occasional scratches.

There may be other sorts of itches that do not have scratches, though they are not psychologically bad or painful. Curiosity may be an itch which, in some cases, where an answer cannot be found, does not have a scratch. Creativity may be an itch with only limited or occasional scratches. The desire for justice may be an itch with only limited or occasional scratches, if any.

It may be there are two kinds of mechanisms; one for itches that have scratches, and one for itches that do not. But the underlying mechanism for itches with scratches may be the same, or have something in common, even though the different specific itches manifest themselves in different kinds of feelings. Similarly, itches without scratches may all be the same in some way, even though the specific manifestations differ. There may be chemical ways to turn off itches in general. There may be psychological ways to turn off itches in general, as when one gets so engrossed in a movie that one forgets one has terrible back pain otherwise. There may be ways to make naturally permanent itches decay or disappear, even without a scratch; that is, there may be ways to turn off itches. There may or may not be ways to develop scratches for any itch.  If satisfying curiosity or learning something difficult ended in an orgasmic kind of way, that might make learning as desirable as sex.  Imagine teenage boys dying to learn things in school, and thinking about it all the time.

But at any rate, it seems odd to me that an itch can have a scratch, whereas it does not seem odd that an itch can decay or disappear. What it might be that makes something serve as a scratch or a climactic resolution to an itch, and how it might work physically and conceptually/logically or structurally, seem to me to be interesting questions or puzzles.