The desire to reduce any body of knowledge to something that fits on a T-shirt -- or, in the case of academic knowledge that subject to testing, on the cuff of a real shirt -- is understandable. So Miss Manners tries to be patient with the nice people who tell her that her noble field is, "after all, just a matter of common sense."

So much for the world's fascinating variety of cultural and ceremonial traditions. So much for the ever-developing interplay of behavior with changing social thought and technology. So much for the ethical and practical task of applying conflicting obligations to the complications of real situations.

Well, common sense certainly helps, Miss Manners admits. You just wouldn't want to be stuck with it alone in a strange situation where you don't want to offend people of whose customs you know little or nothing. But even then, it couldn't hurt. Common sense might have the sense to tell you to admit your ignorance and plead for etiquette instruction instead of bludgeoning your way through, unaware at the horrifying signals you may be sending.

So where is all that common sense in common situations, where it is so badly needed? Miss Manners is exasperated to find it in remarkably short supply when it comes to the simplest and most obvious matters.

Example No. 1: The failure to answer invitations, especially formal ones, usually issued for weddings, is as widespread as it is insulting to the hosts, for whom it has serious consequences.

Therefore, Miss Manners used to think that only the callous would omit doing this.

There are plenty of such folks around, who brazenly tell those kind enough to invite them that they have no way of knowing if they will feel like attending on that date. But there are others who seem genuinely puzzled about what to do. If a reply is not specifically requested, or there is no reply card enclosed, or it comes with a return envelope but no stamp, they figure that no reply is warranted. One Gentle Reader said that since she was not planning to go and the reply card asked for the number of people attending and a meal choice, she had not used it or otherwise answered the invitation.

Example No. 2: People who receive announcements of graduations, engagements, weddings or other happy events, when there is no invitation involved, ask Miss Manners whether they can ignore them or are obliged to give a present as if these are the only possible choices.

Example No. 3: Having received presents, sometimes in the form of checks, the recipients plead that the donors must realize that they are too busy to write letters of thanks, or that they have a year in which to do so, or that it would be offensive to do so at all, as this would imply that the generosity was calculated for an expected return in the way of gratitude.

And these are people who seem to mean well and are actively inquiring about what would be proper. Where, Miss Manners wonders, is their common sense?

Shouldn't it tell them that all social overtures require and deserve an answer? If a friend said, "Do you want to go to the movies tonight?" or a colleague suggested getting a cup of coffee, they might accept or decline -- but would they remain silent?

Do they also greet friends' happy news with silence? Don't they respond with congratulations?

If they send a present, are they ashamed of themselves as selfish if they want to know right away that it arrived and was appreciated?

Etiquette can supply the form and the frills for such responses. But it does need to build on some common sense.

DEAR MISS MANNERS: Is it bad manners to be in a restaurant and, after a meal course, pile up your dishes to make it a bit easier for the waitress? Would they be insulted by this? My wife always does it, and I would think they would appreciate the help and thoughts.

GENTLE READER: Would you be insulted if one of your clients or customers pitched in and started doing your job for you?

Before you say, "Great, then I wouldn't have to do it," Miss Manners asks you to consider the possible results. Suppose that person bungled the job? Suppose the boss caught you foisting off your work?

You and your wife mean well, but piling plates is improper table service. And you wouldn't want the dining-room manager to think that you were reduced to piling up your plates because the waitress had neglected to clear them in good time.

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DEAR MISS MANNERS: Before the Novocain took effect, my dentist of four years and I had a brief conversation about the news of the day in politics. It immediately became clear that we are on different ends of the political spectrum.

Right before she put the rubber dam on me, leaving me speechless, I said, "Well, you are a great dentist, even if we disagree about politics." I hoped that would be the end of it.

It wasn't. She lectured while she worked. She explained her views, berated mine, and assured me that her highly educated friends -- movers and shakers in society -- agreed totally with her.

The high-pitched whir of the drill occasionally drowned her out. Unfortunately, she turned the thing off from time to time. Should I let her know I was offended? Or should I say nothing and chalk it up to the price one must pay for not always flossing thoroughly?

I'm even considering looking for a new dentist -- one recommended by my political party.

GENTLE READER: Check their candidates' smiles first. You wouldn't want to leave a good dentist for a well-intentioned one.

Miss Manners recommends closing your eyes. This is one of the few instances in which appearing to drift off is not rude. Sometimes when the eyes are closed, the ears follow. It might also discourage your dentist from addressing you. If not, you must do what everyone does at the dentist: Keep reminding yourself that, eventually, the session has to come to an end.

DEAR MISS MANNERS: I enjoy giving candy to the small children in my neighborhood on Halloween and admiring their cute costumes, but I am not sure how to respond to the ones who aren't so small and cute. It feels more like a mugging than a social tradition to have my candy snatched in handfuls by hulking masked strangers who are taller than I am.

When I was a child, I was carefully coached to take just one piece of candy and to say "thank you." These "children" don't say anything at all (perhaps to conceal the fact that their voices have changed) and grab as much candy as they can. I'm not sure how to graciously tell them just to take one. I tried "Please leave some for the other children," but they didn't put it back or even say anything in response.

Sadly, I ran out of candy for the cute little diffident ones later in the evening. Should I take some assertiveness training or just wear an intimidating costume next year?

GENTLE READER: No, you get a small tray and offer a fair portion to your visitors, instead of letting them rummage through your total supply.

Miss Manners sympathizes with your attitude, but reminds you that when people are costumed, you are supposed to take them at face value -- masked value, that is. She imagines that you already observe this convention in regard to those cute small children, whom you pretend are big and fierce.

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DEAR MISS MANNERS: I am the mother of a 14-year-old girl who is dating a 14-year-old boy. By "dating," I mean that they send a lot of instant messages and e-mails to each other, they talk on the phone a lot, they go to the movies about once a week with a group of friends, he comes to our house once or twice a week and she goes to his house once or twice a week.

The boy's parents, my husband and I all agree that there should always be a parent at home at whatever house they are at. That is not a problem. What I want to know is what to say to his parents when they appear to be assuming that these kids are dangerous sex maniacs.

"Of course, we like your daughter," they say, "but we're just not comfortable with the amount of time they spend together; we don't want anything to happen."

I don't want anything to happen, either, and I do understand the dangers of raging hormones, but these are intelligent kids who are well chaperoned. Is there any way I can civilly let the boy's parents know that their idea that this relationship is a pregnancy waiting to happen is insulting to my daughter and their son?

GENTLE READER: Not if you give the impression that you believe that only sex maniacs cause pregnancy. Miss Manners is afraid that they would begin to worry about your competence as chaperones.

As the comment you quoted applies to their own teenager as well as to yours, there does not seem to be reason to feel that your daughter's chastity has been impugned. However, if you wish to make the point that she would be incapable of being overcome by passion, you could reply, "Ethan is such a nice boy, I'm sure he wouldn't dream of attacking Caroline's virtue."

Your daughter might not thank you for this defense.

DEAR MISS MANNERS: Do the bride and groom have any obligation to provide or help find baby sitters for out-of-town guests?

My family (including my 3-year-old son) is traveling to participate in a wedding where I am the best man; however, the wedding does not allow children. I am really distressed over what I will do with my son during the wedding and reception. I called the bride and asked her about possible baby sitters and she just said that she didn't know any.

This situation has really dampened my enthusiasm for this wedding; am I just being petty?

GENTLE READER: The bride and the bridegroom do not have an obligation to provide or help find baby sitters. It is thoughtful if they try to anticipate what would make their guests' stay easy and pleasant, and some go to the trouble of hiring a baby sitter to look after all their guests' children, but Miss Manners is afraid that concierge service is not on the required list.

However, your best friend has an obligation to help you out, most especially when you run into difficulty in the course of performing honorable service for him. His fiancC ought to be willing to share responsibility for someone with whom she can expect to become close. Oh, whoops, those are the bride and bridegroom, aren't they?

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