In his December 1965 Los Angeles press conference, Bob Dylan was asked flat-footed questions: “You kinda mumble, you sort of slur,” one reporter began, his mid-Atlantic tone fresh and confident: “Sinatra […] was complaining also about the new modern singers, about enunciation and diction and so forth.”

“The new modern singers are much too sick, nowadays,” Mr. Dylan replied, cheerfully taciturn. “I have a nervous disease,” he elaborated.

“Just what kind of singer are you?” asked another newspapermen.

“A mathematical singer,” Mr. Dylan answered.

Stephen Miller, author of “Conversation: A History of a Declining Art” (Yale University Press, 336 pages, $27.50), would have mixed feelings about Mr. Dylan’s exchanges. Mr. Miller regrets 1960s slang as spoken by Dennis Hopper in “Easy Rider” – “using ‘man’ all the time and speaking in sentence fragments.” Mr. Dylan’s mumbling beats Mr. Hopper’s drawl. On the other hand, Mr. Miller champions “raillery,” a kind of elevated repartee. “To railly well,” he quotes Henry Fielding as saying,”it is absolutely necessary that Kindness must run thro’ all you say.” Mr. Dylan doesn’t like the reporters’ questions, but he’s giving them a good time.

Mr. Dylan fits Mr. Miller’s definition of the “railleur” as one who “enjoys ribbing others and takes no offense at being ribbed.” But Mr. Dylan’s raillery stakes out the gap between his reticent intuition and the journalist’s merely verbal interests. The dialogue recalls Thoreau: “It is a ridiculous demand which England and America make, that you shall speak so that they understand you.”

But Mr. Miller would not consider a press conference a good place for conversation.”Equality is the Life of Conversation,” said Richard Steele, whose Tatler encouraged Mr. Miller’s ideal “Age of Conversation” in 18th-century England. Mr. Miller equates that civilization with civility. He approvingly quotes Swift: “Good manners is the art of making every reasonable person in the company easy, and to be easy ourselves.” As a corollary, Mr. Miller offers that “politeness signified a way of thinking as well as acting, a dislike of extremes in thought.”

In defining conversation so narrowly,Mr. Miller reacts to a specific contemporary concern: that the United States is doomed in quarreling. He laments blogs,”Oprah,” and a future of “angry narcissists.” He soundly damns the twin poles of contemporary dullness: “Don’t be judgmental!” at one end, and “Express yourself!” at the other. But Mr. Miller’s more worthy opponent is Romanticism. He sees the death of the Enlightenment in terms of a decline in conversation.When, by the mid-18th century, London’s literati head for the Lake District and the her mitage, Mr. Miller is already on the defensive. He stands with Samuel Johnson, who “attacks rural solitude” and who writes, “Many have no happier moments than those that they pass in solitude, abandoned to their own imagination, which sometimes puts scepters in their hands or mitres on their heads, … and gluts them with every change of visionary luxury.”

Mr. Miller reads “visionary luxury” as “mental extravagance.” He regrets the poets and tourists who, instead of conversation, “admired the sounds of the natural world, especially the sound of running water, which was a symbol of the creative imagination.” Although he risks sounding pat, Mr. Miller lands his blows.

“The sublime is a world without wit and raillery,” he writes. Mr. Miller dislikes solemn moods, whether they come from marijuana or from vistas. But as he carries his attack deep into Romantic territory, he becomes less convincing. Cut off from the patent brilliance of the Johnsonian milieu, his advocacy of conversation sounds willful. Is it cogent to write, about Whitman, that “Barbaric yawps are not what the 18th-century writers on conversation had in mind”? If shy Thomas Gray, author of the “Elegy Written in a Country Church Yard,” hoped to continue, in “The Bard: A Pindaric Ode,” the tradition of celebrating “true virtue and valor in immortal strains,” should we then conclude, with Mr. Miller, that “Gray was neo-Spartan like Rousseau”?

Mr. Miller confuses disposition with virtue. He quotes Gray’s friend Horace Walpole, who writes that Gray “is the worst company in the world – from a melancholy turn, from living reclusively, and from a little too much dignity, he never converses easily.” The conversable world has always intimidated some of its finest souls; it seems a shame to identify civilization with conversation so strongly as to leave its geniuses out in the cold. What Dylan and Thoreau had in their heads may not have been fit table talk, but it was good. It did not create the “angry narcissism” that Mr. Miller ultimately fears.

One of the most poignant anecdotes in Mr. Miller’s book concerns James Boswell’s evening of July 4, 1786, when he could find no dinner companion. He tried several coffeehouses, but found no talk.”When I got out into the streets again I was so depressed that the tears run down my cheeks,” he recorded in his diary. Every living person has had such a night, whether because of a lack of companions, or because of some internal failure. Although Mr. Miller well acknowledges the fragility of any conversation, he does not look very hard at the gum of internal experience, where potential conversations live and die. Many want to talk who cannot. This would be the territory of a writer who would risk “an extreme of thought,” or a “mental extravagance.” In successfully describing a sea change in attitudes toward conversation, Mr. Miller gives the false impression that conversation can subsist by exterior factors alone.