IN CHARLOTTESVILLE, said ex-president William Howard Taft after he had once lectured there, "they still talked of Mr. Jefferson as though he were in the next room."

The quotation is one of Dumas Malone's favorites; and when Malone himself speaks of "Mr. Jefferson," it does not sound at all strange or even reverential, certainly not on a hot Charlottesville afternoon in the booklined study of Malone's modest Lewis Mountain Road bungalow. Mr. Jefferson's presence, if not precisely located in the next room, can indeed be felt emanating from the nearby summit of his "little mountain," where today he spiritually broods over his community in a way that no Whig or Tory magnate ever overshadowed his village in 18th-century Wiltshire.

It is early June, and Malone is in good form, showing off his crinkling charm and zest for conversation -- he is 89 and almost blind, but talks a blue streak and clearly has forgotten nothing he ever learned about American history. Any ungracious thoughts the visitor might have had about the humidity or the repetitiousness of the surrounding university architecture, an unending pageant of red brick and white pillars not entirely atoned for by the Palladian elegance of the famous rotunda and pavilions, were dissolved earlier that day on the drive to the top of Monticello. There, 800 feet above the toylike town and campus, the eye revels in one of the great vistas of the North American continent: to the east, rolling fields stretch out toward Richmond and the Tidewater country; to the west, the massif of the Blue Ridge marches across the horizon, proclaiming the nation's first western frontier. Malone savors the memory of this prospect, and it sadly can now only be a memory for him, but he captures it perfectly in Jeffersonian terms: "His eye like his mind sought the extended view."

"When I first came here in 1923, they knew surprisingly little about Jefferson -- here and everywhere," marvels Malone. "Only Franklin can touch him, and Franklin really was pre-national. Franklin never made it into our national pantheon -- Washington, Jefferson and Lincoln. Franklin had a certain earthiness; the others had nobility." And here the distinguished biographer-in-residence of the University of Virginia interrupts himself to tell a slightly resque story about Ben Franklin: "Sam Morison used to say that 'Ben Franklin's keel was laid in Nantucket, but he was launched in Boston.'" And Malone doubles up with hoots of laughter and slaps his thigh just as he must have 70 years ago when as a Georgia minister's son he attended Emory and later Yale to study first divinity and then American history, one of many bright Southern boys with beautiful manners and slender purses who went on to academic distinction in the North; from Emory alone, recounts Malone proudly, came C. Vann Woodward, Fletcher Green and David Potter.

It was of course Robert E. Lee, the South's "deathless martyr of our kingdom of the twilight" -- the eulogy is Jefferson Davis' -- who triggered the interest in history. "Lee was my boyhood hero. We held Jefferson in high esteem, but I don't remember anything special in my family about him. In fact, my parents would have viewed his religion with trepidation, although they were broad-minded for their time and place. My mother was a pioneer suffragist." Malone explains. "Southerners have a feeling for history. They were hurt by history. To us, history was the Civil War. My grandfather was at the first battle of Manassas." Malone pauses and then adds quickly with more laughter, "and that of course established me in Virginia."

Malone suddenly decides to show off his Visualtex reading machine -- there is another one in his office at the Alderman Library, but this is the one on which most of The Sage of Monticello was composed. The equipment was the gift of an admiring Thomas Jefferson Foundation, the private nonprofit corporation presided over by James Bear Jr. that operates Monticello. "I'm not much of a gadgeteer, but Mr. Jefferson certainly was. You know his writing machine that copied his letters. The way this works is that my research assistant [Steven H. Hochman, recently appointed assistant to former president Jimmy Carter for his memoirs] tapes books and articles. I listen to the tapes and using this thing write a few pages. My secretary [Katherine M. Sargeant] then transcribes them. I could not have done it without their help, and that is why I have dedicated the new volume to them." And proceeding to demonstrate how the device works, he writes a few words on a legal pad. The machine magnifies them onto a viewer, which Malone, peering, can just read. He accepts his affliction, and his age, philosophically. "The seventies are wonderful. You don't have to read doctoral dissertations or attend committee meetings. In the eighties you begin to crack around the edges." A principal regret is that he can no longer go swimming at his West Falmouth, Massachusetts, summer home. "I can't see the shore and might swim off to sea. But as you see one of the few things I can do is talk."

Malone was born in 1892, a year that produced Edna St. Vincent Millay, John Peale Bishop and Archibald MacLeish. His generation smacked right into World War I. He won't say how, but the desire to be a minister like his father left him during the war years, when he served in the U.S. Marines. "Being a professional good man somehow didn't appeal to me." So he returned to Yale to take up the formal study of history. There have been a few changes in the intervening years. "I've seen the coming of television, radio, the airplane, the automobile. I've seen the whole thing -- I've seen a helluva lot. The technological stuff is wonderful, but it's got ahead of everything. Human nature hasn't changed at all."

In the course of a very long life, Malone has enjoyed several careers: teacher (Yale, Columbia, Virginia), university press director (Harvard), editor (The Dictionary of American Biography -- "the greatest enterprise of cooperative scholarship ever undertaken in this country") and, of course, biographer. He has seen historical fashions come and go. He has probably known more American historians than any other scholar now living. What has he learned? "There is no substitute for staying close to the primary sources," he affirms.

The talk turns to contemporary politics. "If Mr. Jefferson were alive today, he would be appalled by the bigness of things. He would not like the way the dollar has become the measure of all things. Nobody ever said more against the evils of the national debt. He would naturally advocate the decentralization of government. But he would argue against the ushering in of a new era of intolerance and he would tell President Reagan not to throw out the baby with the bath."

Malone's colleagues from the university and at least some representatives of the Jefferson establishment -- the Foundation, the Jefferson Papers project at Princeton, the Library of Congress, the American Philosophical Society -- were planning a dinner for him in the rotunda at the university to celebrate the publication of the concluding volume of the biography. Malone guessed it would be his lot to toast "the immortal memory" of Mr. Jefferson, whose stirring words and pragmatic philosophy still move Americans, and not just scholars, to notions of the public good. What was Malone planning to say? He did not know exactly, but he would say that even after 40 years of research, he "could not hope to have done full justice to a virtually inexhaustible subject." He would say, he guessed, that Jefferson expected his fellow citizens to be "more reasonable than they are likely to be . . . he made too little allowance for emotions and counted too much on the sufficiency of reason." He would say that Jefferson "to all who cherish freedom and abhor tyranny in any form is an abiding symbol of the hope that springs eternal."