A 6-year-old boy, his left leg amputated in surgery, wakes up in a pediatric hospital in Philadelphia to announce that his missing leg is under his bed.

The simple truth is that the leg is not under his bed. But what good is the truth? He needs a doctor who is less than truthful, who will countenance the boy's self-deception until he can accept the loss of his leg. The better the liar, the better the doctor. For a while, at least, the leg is underneath the bed. The lie is a truth.

A president of the United States says there is a "Welfare Queen" who drives a Cadillac, wears furs and boldly cheats the welfare system. She steals money from hard-working American taxpayers.

The simple truth is that the president is right. There was a woman in Chicago charged in 1977 by the Illinois Pblic Aid Department with using 26 aliases to defraud the welfare system out of more than $150,000. But what good is the truth? There is no evidence that the welfare queen is typical. The president, like others before him, uses truth to deceive. The more little truths he dredges up, the more he misleads the American people. The truth is a lie.

The truth, the whole truth and nothing but truth is not nearly as virtuous as it's cracked up to be. There are mean, self-righteous, uncaring people who peddle mean little truths. Without some artful and caring lying, doctors will demoralize their patients, lovers will scare off their partners and society as a whole will become an uncultured collision of plain- speaking brutes.

If, like George Washington in his apocryphal encounter with the cherry tree, we cannot tell a lie, we are doomed.

That was the consensus last weekend in New York City at a symposium of nationally known physicians, psychoanalysts, writers and a pollster. On a sunny spring Saturday, they met together in a stuffy, crowded auditorium at Columbia University. Out of more than six hours of lecture, argument and harangue emerged some persuasive insights into how and why we Americans tell each other such painful private truths and such divisive public lies.

In intimate relationships -- as between doctor and patient or husband and wife -- it has become fashionable to dump the unvarnished truth. A truthful doctor says, "I'm sorry, but this kind of cancer is terminal. You have a month to live. There's nothing I can do." A truthful spouse says, "I've been sleeping with somebody else. I don't love you and I haven't loved you for years."

The doctor and the spouse may be insensitive, they may be absolving themselves of their responsibilities as human beings, but -- like little George Washington -- they can comfort themselves with their allegiance to truth.

In public life, presidents routinely misrepresent expected budget deficits, increasing numbers of businessmen fraudulently declare bankruptcy and more taxpayers than ever cheat on their income taxes. A well-told lie in public life saves money or saves face. While lies in private life are told to individuals, public lies are told to faceless groups, the government or to the "enemy." That somehow seems to makes it less of a lie.

According to last weekend's symposium, entitled "Truth and Its Limits: Public and Private Domains," behind much of America's private truth-dumping and public lying lurks a dangerous misunderstanding of when truth should be the highest value and when it should be sacrificed for love and compassion.

The symposium's rule of thumb is that truth -- a slavish fidelity between actual events and what is said about those events -- should become less important as relationships between people grow more intimate and complex. The doctor treating the little boy with an amputated leg has responsibility for the child's life and future mental health. A strict adherence to the truth, which would require telling the boy that his leg isn't underneath the bed, would be a mindless betrayal.

"Truth-dumping," said Dr. Willard Gaylin, a professor of psychiatry at Columbia University and a speaker at the symposium, "is a derogation of the complexity of human relationships. It is morally reprehensible."

As the distance between people increases, however, truth takes on an ever-increasing importance. Unless they can count on hearing the truth, strangers have no reason to trust each other. Truth is the thread that knits together nations, especially those that depend on the informed consent of the governed. A president, for example, who routinely lies (or uses little truths to tell larger lies) devalues truth -- the one currency that makes politics, business and nearly all social interaction possible.

Many Americans seem to have gotten all of this backward, bruising their friends and lovers with the truth and at the same time crippling society with lies. The reasons why, according to the symposium, have to do with a mistakenly literal conception of truth.

The truth doesn't stand up in a room and command that people obey it. It is not an immutable essence that, like a Platonic idea, exists in its own independent realm. If a truth tree were chopped down in the forest, and no one heard it fall, it would not fall. But many Americans can't seem to understand this, Gaylin argued. He said there is a "tyranny of truth" that ignores the way human beings learn.

Gaylin said that children pick up "truths" about themselves that influence their entire adult lives but which, in actuality, may be lies. A child, for example, who's told that he is fat may devote his adult life to staying skinny, to disproving the "truth" of his obesity.

"You can spot these ex-fatties," Gaylin said, "because they are trying to fool everybody. They are trying to pretend they're not fat."

Gaylin's point is that personal truth has no necessary connection to objective reality. It simply doesn't matter whether or not a child was, in fact, fat (or ugly or stupid or cursed with big ears) when he accepted the "truth" that haunts him his entire life.

Truth, in personal relations, is one virtue among many. The job of a lover is to give love, not truth. The job of a doctor is to heal, not dispense truth. If the truth helps, fine, but lying can be equally virtuous, according to Dr. Robert Michels, chairman of the department of psychiatry at Cornell University.

Michels said the "creative and compassionate use of lying" can enrich human life far more than "narrow people who always tell their dirty little truths."

Blind fealty to truth, author Francine duPlessix Gray told the symposium, is a form of "sadism."

Gray said that an ebb of manners and civility has coincided with a flood of truthful "psycho-babble" about feelings and sexual performance. This, Gray claimed, has "turned American dinner parties into group therapeutic horror shows."

In medicine, bio-ethicists have in recent years reached a consensus calling for a doctor to tell patients the complete truth about illnesses. Medical societies and medical schools now criticize as unethical doctors who withhold crucial information from patients "for their own good." Some states have passed laws spelling out a patient's right to know the truth.

This rush toward total candor between doctor and patient, however, is doing more harm than good, according to Dr. Arnold Relman, a professor of medicine at Harvard Medical School and editor of the nation's most prestigious medical publication, The New England Journal of Medicine.

"It does violence to reality to imagine it is possible (for a doctor) to tell the whole truth and nothing but the truth to a patient and to believe that this is what the patient wants," Relman told the symposium. "The attitude that says the truth is the important thing, not the patient, allows for a lot of damage."

While acknowledging that doctors have for years abused their patient's rights by paternalistically withholding information, Relman argued against a knee-jerk truth barrage.

"In my experience, patients do not want to hear about everything that could possibly go wrong or the limitations of their doctor's understanding of their case. The sicker the patient, the more readily he accepts the knowledge gap. Patients are often frightened, even terrorized, by information thrust on them by doctors who use a truth-at-all-costs paradigm," Relman said.

According to Relman, dumping the truth on a patient without regard for the consequences and then walking away is an easy way to be lousy doctor.

Although Relman failed to mention it, a major reason doctors feel a compunction to dump the truth on their patients is fear of malpractice suits. The possible intrusion of a judge, jury, lawyers and insurance companies into their practices has probably scared many doctors away from well-intentioned lying.

As the number of witnesses to a lie increases, as the distance between the liar and the lie-ee grows, the human context of love, friendship or healing is lost. It becomes impossible for lies to serve benevolent purposes. Among strangers, the common good can only be served by the truth.

Yet, as pollster Daniel Yankelovich pointed out at the symposium, the same distance that forces strangers to rely on the truth also makes it possible for public liars to lie with impunity. These liars don't know to whom they are lying, Yankelovich said, so they don't feel guilty about it.

Because of this "distancing" -- between government officials and voters, mass media and their audiences, Americans and Russians -- Yankelovich argued that "deception loses its invidious character." Instead of seeing their lies as affronts to individuals, Yankelovich said many "elites" have a "simple sense of a mysterious mass out there to be manipulated."

As a further encouragment to public lying, Yankelovich said government leaders and news media subscribe to "an elite code of conduct." That code, he claimed, anoints government officials and reporters with a "moral legitimacy" for whatever they do and teaches them to believe in the "kill."

The kill, Yankelovich said, is "a primitive notion of winning that is very deep in the American ethos."

When two elites, such as the government and the news media, face off against each other, Yankelovich said, the objective is a "kill" and the first casualty is usually the truth. The pollster pointed to the recent CBS documentary, "People Like Us," in which the network featured four case studies of how the Reagan administration is wreaking havoc on poor people.

In one of the four cases, CBS misled its viewers. Administration cutbacks did not force a Wisconsin mother to move her comatose child out of their home, as the program implied. But after the documentary aired, the White House claimed that the entire program was misleading. CBS stood by its story. The adversaries had more important things to worry about than the truth.

Even as the anointed elites snip away at the truths that hold the republic together, everyday Americans, in Yankelovich's view, are contributing to the acceptability of public lying by "destigmatizing taboos" in other social matters.

The pollster pointed to the explosion in the number of bankruptcies (which more than doubled from 210,000 in 1980 to 450,000 last year), in the number of divorces (since 1965 there has been a 400 percent increase in divorce among people married 20 years or longer) and in the number of illegitimate births (one out of six babies born in 1980 was illegitimate, a 50 percent increase in 10 years).

With more and more Americans casting off their aging spouses, raising illegitimate children and getting divorced, Yankelovich hints that they will find it painless and rewarding to lie to each other in public life -- especially since the elites seem to be getting away with it.

What then of the future? Are Americans condemned to pummel their loved ones with cruel truths? Will we lie to each other so much in public life that the trains wan on't run on time?

The New York symposium on truthing and lying made no forecast. It ended, however, on an upbeat, pro-lying note. Dr. Arnold Cooper, president of the American Psychoanalytic Association and the symposium's last speaker, stood up in the sweaty auditorium and quoted writer Ring Lardner:

"I have never lied save to shield a woman or myself."