The subject of manners once seemed worthy of serious attention. The authors of the Talmud took up such topics as burping, yawning and bad breath. Erasmus wrote the 16th-century equivalent of a best seller on civility, and Edmund Burke considered manners more important than laws.

But somewhere between the Renaissance and the late 20th century, the topic got a bad name. Manners came to be viewed as trivial, hypocritical and superficial. Heavy thinkers abandoned manners to the authors of etiquette books, with their fussing about finger bowls and the evils of blowing on soup.Now an interest in the subject, which once preoccupied the middle classes, is back in vogue, and not just among politicians like New York City Mayor Rudolph Giuliani, who earlier this week went so far as to invoke Plato in his continuing quest to make the city a more orderly, civil and, well, mannerly place.

University of Pennsylvania president Judith Rodin has convened a 48-member national commission, made up heavily of academics, that is now in the midst of a three- to five-year study of what some believe has been an explosion of incivility degrading the quality of public life.

At Johns Hopkins University, P.M. Forni, a professor of Italian literature and culture, has organized a wide-ranging project that includes a course on civility, manners and politeness. It also includes research on civility in schools and in health care, and efforts to encourage scholarly work in the field.

Last fall, the university offered the course not only to its own undergraduates but also to inmates at a maximum security prison in Jessup, Md. Having spent the semester study-ing texts like Erving Goffman's "Interaction Ritual," both groups came together at the end to discuss what they had learned.

And next month, Johns Hopkins plans to hold a three-day international symposium entitled "Reassessing Civility: Forms and Values at the End of the Century," with speakers ranging from historians who have written on manners to Judith Martin, the author of the Miss Manners columns and books.

"Manners were expelled from respectable scholarly thinking: `Who would be interested in a stupid thing like that?' " Martin said. "Never mind that the answers are Burke, Mill, Emerson, Aristotle, Cicero, Castiglione, Erasmus, Locke."

There is indeed a long tradition of serious writing on manners, not the least of which were three centuries of "courtesy books" originally written to instruct young princes but later directed to the sons of the upper classes.

One of the best known of the genre was Erasmus' "De Civilitate Morum Puerilium" ("On Civility in Boys"), first published in 1526, which went into more than 130 editions and covered everything from dental hygiene and the importance of clean fingernails at the dinner table to when and how to spit.

A wide-eyed look suggests stupidity, Erasmus advised. If mucus falls on the ground while blowing one's nose with two fingers, step on it, fast. When offered a communal tankard, wipe your mouth first. If food sticks to your teeth, remove it (with a quill or a toothpick, not a knife).

"The whole idea of manners was linked to civilization," said Richard L. Bushman, a Columbia University historian and the author of "The Refinement of America" (Alfred A. Knopf, 1992). "It would be listed right along with the growth of art, science and law as a sign that we were civilized."

But that view changed, at least among scholars. Michael Curtin, a historian in Oakland, Calif., has traced the shift to the late-18th and early-19th centuries, when he believes the longtime association between manners and morals was irrevocably broken.

But in 1978, a history of manners that was then 40 years old, "The Civilizing Process" (Blackwell) by Norbert Elias, was published in English for the first time. Many scholars say has since inspired new interest in manners and helped transform the way they are seen.