We all know these things exist. So why not talk about them?"

For generations untold, this was the argument with which young people traditionally attacked their elders for ruling certain matters off-limits for conversation.

It is supposed to be simply devastating reasoning, because it demonstrates that the young are not only so insightful as to discover aspects of life that had been previously overlooked, but ruthlessly courageous for bringing them out into the open.

Miss Manners has always considered this exercise highly amusing.

Parents are generally wilier than their children suppose -- they can hardly be less so -- and youth is too naive to understand that not bringing everything out in the open is one of the techniques that make civilized life possible. So it was always easy to hoodwink the young into believing that the elders' silence actually covered a lack of adventurousness.

Thus, the same young people who denounced the hypocrisy of keeping silent about reality also fell for the trick, by believing, deep down in their hearts, that the real reason the elder generation refused to discuss the seamier emotions was that it didn't have any.

It was such a useful arrangement, allowing grown-ups to retain their dignity as well as protecting whatever wickedness they happened to practice, that it seems a shame to Miss Manners that the jig is up. What ought to be today's reigning generation was the one that actually fell for that age-old argument and made official the policy of expressing whatever was on the mind.

The confessions of wickedness turned out to be a lot less interesting than we had all imagined. But the real shock was that what came pouring out, once the floodgates were open, was not only the expected bragging and whining, but a rather primitive curiosity about others, along with an offensive urge to proselytize.

Now that there is no difference between having a thought and expressing it, no subject is considered too personal for inquiry, and no matter off-limits for offering advice.

In Miss Manners' mail, there are complaints from people who are constantly asked how old they are, how they make a living, how good a living it is, when they plan to get married, whether their pregnancies were planned, whether they adopted children because they were unable to have them and why the biological mother gave them up, whether they realize they are overweight, why they don't do something about their hair, whether they have had face lifts and how much they paid for just about everything they own.

Not surprisingly, all of these people are angered by inquiries they consider at best to be nosy and at worst cruel. Nor do they consider the unsolicited advice that usually follows to be useful or kindly meant.

Why, then, is it such a common practice now to indulge in conversation that is certain to offend? Wouldn't you think that do-gooders might be willing to wait for confidences to be volunteered or assistance requested?

Here is one response from a Gentle Reader who believes that another of Miss Manners' Gentle Readers was wrong to be offended by constant inquiries about whether she was nursing her baby. "This," she says of what she considers to be an unwarranted complaint, "from someone who presumably just returned from a hospital obstetrics floor, where it is the nurses' mission to inquire into one's daily elimination and other personal habits, even if it means interrupting a patient in a phone booth to do it, and where the young mother gave birth to her precious bundle in the presence of numerous uniform-clad strangers she had met only hours, some of them minutes, before. Hardly a private affair."

The practice of nursing babies, which the second reader goes on to laud, is not the issue here; for all Miss Manners knows, the first reader may be an enthusiastic believer in it as well. The issue is whether there is any form of conversation that is properly off limits to nonintimates.

That there must be is very difficult to explain to someone who sees no difference between discussing one's elimination with one's nurse and doing so socially; who feels that anyone who exposes herself to an obstetrical team has forfeited the right to demand privacy from others.

It apparently takes a great deal of sophistication to understand that there indeed should be a difference between thinking or knowing something and saying it.

Q. These days, most brides-to-be are working and have little enough time as it is. If it would be of great help, would it still be considered in bad taste to have someone other than the bride address the wedding invitations?

A. Wherever did you get the idea that the bride was supposed to address the wedding invitations? In spite of all those brides who run around saying, "It's my wedding, isn't it?" to justify ignoring the wishes of everybody else concerned, it is not usually the bride who issues invitations; her parents do.

In any case, social law demands only that the invitations be addressed by hand. It does not have an investigation department to check to see whose hand.

Q. How can one let friends know that one has completed a university course and graduated? My case may be unusual in that I'm a senior citizen and, to my surprise, in the final term made the dean's list.

My friends know what I've been up to for the past few years, so I'd like to let them know about the degree, yet don't want them to feel it necessary to send a gift. But I don't want to be presumptuous and tell them, "No gifts, please."

A. Why make any presumptions at all, other than that your friends would be pleased to hear of your success (by letter or by graduation announcement with your card enclosed)? Miss Manners is pleased, and she doesn't even know you.