AT THE BEGINNING of this excellent new critical biography, Park Honan nails his colors to the mast: an understanding of Arnold, he writes, "is more useful to us than an understanding of any other Englishman of the last century." And, he might reasonably have added, more difficult to come by. As our own day swings round to recognizing the force of Arnold's call for a disinterested critical approach to intellectual and artistic values, we see that behind his clear intelligence lies one of the great personal enigmas in English literature. And, whatever formalist critics may say, we need to know something of the psychological promptings for his pronouncements if we are to make reasonable assessments of them.

There has already been a mysterious split apparent between the glacial, assured urbanity of Arnold's essays and the fretful romantic intensity of his poetry. Yet even that poetry can seem remote: the narrator of "Dover Beach" observes life through a window, in "Resignation" the Poet sees it from behind the protection of a gate, and the Scholar Gipsy is detached in both time and space from those around him. where is Arnold himself, we want to ask, what is the center of his being? What is the cause of his nearly pathological urge to withdraw?

Until now the materials for an Arnold biography have been severely limited, largely because he characteristically asked that none be written, so that his family has hesitated to release what it controlled. Honan has at last broken into many of the unpublished sources, and he says that three-quarters of the biographical material in this book has not appeared before.

When Lionel Trilling wrote his masterly study of Arnold some 40 years ago he gave a passing nod to the problem by calling his critical book "a biography of Arnold's mind." Honan follows his lead in giving the balance of his study to criticism rather than the outward events of Arnold's life. The criticism is sound, but not surprisingly it is the new biographical information that catches the eye. Although it does not radically change our attitude toward Arnold, it wonderfully fills many gaps.

We learn more about his fervent relationship with his beloved sister Jane ("K"); Honan says sensibly that there is no evidence of incest, but there was surely something abnormal about his anguished reproaches to her upon her engagement, his refusal to go to her wedding and the family's concealment of the fact, and the speed with which he became engaged himself a day or two after her marriage. There is new information here about the intensity of his relations with his children, as if he were making up in closeness for his distance from his own father. We learn of the agony of the heavy irons he wore as a boy to straighten his legs; his pride in his appearance (Henry James thought him red and coarse, but James was not easy to please in such matters); his unsuccessful battle against weight (before his death he weighed nearly 270 pounds); his surprising addiction to alcohol and scatalogical language; the lack of humor he displayed to his friends; his tone-deafness and Philistine failure to appreciate visual art.

Above all this is the first biography to identify "Marguerite," to whom he adddressed some ardent love poems but whose very existence has often been questioned. She was a beautiful young neighbor in the Lake District, Mary Claude, who had been born in a French Protestant community in Berlin. Nothing scandalous occurred, readers will be sorry to hear. He fell in love with her when he was 25, arranged to meet her (probably with innocent intentions) in Switzerland, he was teased by his friends when she failed to appear, and several years later wrote a series of poems about her. Mlle. Claude remained unmarried, but that fact apparently had nothing to do with Arnold. It is an indication of the insubstantiality of our knowledge of Arnold previously that it was so easy to believe the family story that Marguerite was not even a living girl but only the poetic projection of the unfettered side of his nature.

Unfortunately, there is little new evidence here of his feelings about his father, the great and forbidding headmaster, Thomas Arnold, whom Matthew found both admirable and totally uncongenial, although he adored his mother extravagantly. As Trilling wrote of "Sohrab and Rustum," "it is almost impossible not to find . . . at least a shadowy personal significance" in that story of the son crushed by the weight of his father's reputation and at last unwittingly killed by him. In spite of his professions of love, it took Matthew nearly a quarter of a century to finish his elegy on his father, "Rugby Chapel," and after all that time it is still one of the chilliest tributes in English poetry. Surely, the source of many of Matthew's difficulties lies hidden in his life obscured by the shadow of the great man.

When Park Honan wishes to be, he is wonderfully illuminating about the works and their unacknowledged connection with the events of Arnold's life, as in the discussion of Frienship's Garland and its partial origin in the character of William Forster, the husband of his sister Jane, a man for whom Arnold felt an Olympian distaste. More often, Honan prefers to speak of Arnold's life and works separately, allowing the reader to make his own connections, which may put a burden on anyone who does not remember the writings in detail. For a reader primarily interested in the hidden sources of action and creation, this biography leaves some questions unanswered and some coincidences unremarked. Although he never says so, I suspect that the author faintly distrusts psychological interpretation of literature, and it is to his credit that he, therefore, keeps clear of it. But his combination of straightforward record of Arnold's life and clear-headed analysis of his poetry and essays is a remarkable work not apt to be superseded in our generation.