JAMES AGEE, in a celebrated essay called "Comedy's Greatest Era," published 36 years ago in Life magazine, cited Mack Sennett's opinion of Charlie Chaplin: "Oh, well, he's just the greatest artist that ever lived." Agee agreed, compared Chaplin with God, and went on to write that "the Tramp is as centrally representative of humanity, as many- sided and as mysterious, as Hamlet, and it seems unlikely that any dancer or actor can ever have excelled him in eloquence, variety, or poignancy of motion."

Those words were published in 1949, just after the failure of Monsieur Verdoux, when Chaplin's reputation was already in eclipse, an unlucky victim of both lurid publicity attendant on his incautious sexual pecadillos and his temperamental inability (paraphrasing Lillian Hellman) to trim his sails to suit the temper of the times. (He was an unrepentant friend of the Soviet Union.)

In 1952 Chaplin went into semi-involuntary exile from the United States, his adopted homeland, and was not to return until 1972 when he received a much belated special Oscar from the Motion Picture Academy in Hollywood. In the intervening years, critics, with several notable exceptions, ratified the verdict of the Cold War inquisitors by concluding that, after all, his was an inferior talent, a poor second to that of Buster Keaton or even Harold Lloyd. Keaton's comedy, it was said, was cool, cerebral, ironic, and therefore modern; Chaplin's was weepy, visceral, sentimental, and therefore distinctly old-fashioned.

But if anything is certain, it is that critical opinion eventually changes. (J. Hoberman has recently argued in the Village Voice, for example, that if post-modernism can be partially characterized by a blurring of the distinction between high and popular culture, Chaplin, universally acknowledged in his lifetime to be a consummate artist, was the first truly post-modern figure.) Therefore it is not surprising that we are now in the midst of a modest Chaplin revival. Last year an extensive retrospective of his films toured the country, and a truly remarkable three-part compilation of outtakes and lost and neglected footage, put together by Kevin Brownlow and David Gill and called The Unknown Chaplin, played festivals and art houses. There are several Chaplin biographies reportedly in the works. The first out of the starting gate is David Robinson's ambitious volume, simply entitled Chaplin: His Life and Art.

UNLIKE PREVIOUS biographers, Robinson, who is the film critic for The Times of London, has been granted access to Chaplin's private papers by Oona O'Neill Chaplin. This, then, if not exactly an authorized biography, is at least one that is presumably not unwelcome to the Chaplin estate. Robinson's passion for Chaplin is evident on every page, sometimes amusingly so when it is transparently at war with his distaste for Chaplin's penchant for communists and teen-age girls.

This passion, however, is in no way misplaced. There is no question that Chaplin was a screen artist of the first rank, arguably the greatest who ever lived, and a serious biographical effort such as this one is no more than his due -- in fact, it is long overdue. Robinson has produced a meticulously researched, comprehensive work that is likely to stand alone for many years as the definitive life of Chaplin with which subsequent efforts will be invidiously compared. His approach is sensible and straightforward. Avoiding fanciful psychologizing, he provides an unadorned and circumstantial account of Chaplin's rise from a Dickensian childhood in the slums of London to the pinnacle of world renown. (Had Chaplin been so inclined, he could have anticipated by four decades the Beatles' claim to greater fame than Jesus Christ; the only man he ever met who had never seen his movies was Gandhi.)

Quoting extensively from private correspondence, contemporary accounts, and interviews with Chaplin, family and friends, Robinson draws a picture of a man of wildly contradictory parts: at once enormously vain and pathetically insecure; intensely private but addicted to the adulation of the crowd; a lover of the common man who luxuriated in the pleasures of wealth and attentions of the wealthy; an intuitive artist who improvised his sketches, yet shot take after take in search of a perfection that remained elusive. (On The Kid, he indulged himself in an astounding shooting ratio of 53 feet shot to one foot used.) The book is particularly good on Chaplin's early years and the British music- hall tradition in which he was trained. His private and professional lives each gets its due; Robinson provides the best account to date of how Chaplin worked. Of particular note are an extensive appendix that includes three Keystone scenarios demonstrating the development of Chaplin's craft and a synopsis of some 1,900 pages of FBI documents on Chaplin, a monument to J. Edgar Hoover's 50-year vendetta against the comedian.

During his lifetime, the Chaplin legend was fed by newspaper headlines, sensationalism, and gossip; it was sustained by Chaplin's own reticence in the face of a blizzard of quickie books and articles by discarded lovers, sometime friends, and casual acquaintances. One of the great services that Robinson's book performs is to sift fact from fiction, and at long last to shine the light of scholarship on Chaplin's life.