WE COULD HARDLY, in our business, think of advertising as being anything other than good for you. It supports us. It lets others get their messages to the public. Most advertising seems to us to be socially useful. Besides occasionally communicating an idea, ads tell people what goods and services are available where and at what price. So we have a little difficulty coming to grips with the inability of some professional organizations - most notably those of lawyers, doctors and dentists - to square their ideas about advertising with the First Amendment.

Lawyers in particular are having trouble accepting the fact that the Supreme Court has said they have a constitutional right to advertise. Both the American Bar Association and a committee of the Maryland Court of Appeals have drawn up rules to regulate advertising to lawyers. These rules seem to us - and to the Justice Department - to defy, rather than comply with, that Court decision. We don't propose to argue about the legalities, the department is doing that admirably. But we do have some thoughts about the fears that underlie the codes of conduct that bar many professional prople from advertising their services and prices.

There are, no doubt, charlatans practicing medicine, law, dentistry and the rest. One of the fears of the "good" professionals, as we understand it, is that advertising will permit these peoples to con the public into buying their services. Price-cutting - wills for $24.50: appendectomies for $99.99 - will result in badly written legal documents and shoddy operations, or so the argument goes. Other advertising gimmicks, it is said, will let John Doe convince you he can do a better job for you than Richard Roe can when, if vact, he can't.

Such arguments, is seems to us, underestimate the public's sophistication about advertising. These days children begin learning at a very early age tha difference between reality and puffery and also the frequent correlation between quality and price. (If you don't think so, corss-examine them on the inundation of toy ads on television right now.) Not many people are going to be fooled by ads praising some professional person's competence or offering bargain basement prices for complicated work. Most people have learned by this time that you get in quality about what you pay for.

Professional organizations should not be holding back advertising that makes known the availability and cost of services. They should, instead, be improving their internal mechanisms for rooting out their own charlatans and incompetents. These are the people who defraud the public even without advertising. And they are going to continue doing so whether or not they can advertise. Indeed, advertising may help expose them; anytime you see a lawyer advertising a contested divorce for, say, $100, you ought to be very skeptical.

We will concede that some of the ads placed by doctors and dentists in recent weeks have not been in what you would call good taste. But we have also noticed that the prices of some routine services - especially those of lawyers on things like uncontested divorces - have declined. That is part of what advertising is all about; competition. It is also about letting people know what services are available. All the evidence suggests that there is large reservoir of work - legal, medical and dental - to be done but there if people knew where to get it at a price they could afford. The country can put up with some distasteful ads if a larger number help meet needs that are currently going unfilled.