It was my exceptional good fortune to spend several hours last week with Sir Alec Guinness -- not, alas, with the great gentleman himself, but with galley proofs of his forthcoming memoir "Blessings in Disguise." A few weeks hence I shall address the particular and manifold virtues of that book in a review, but at the moment it raises another matter. "Blessings in Disguise" is a vivid and telling reminder that there are more ways to tell one's life story than there are to skin a cat, and that the memoir is as flexible and unpredictable as any other form of writing.

This reflection was caused by Sir Alec's decision, at first glance a surprising one, not to include certain major episodes in his story. Though he has performed in some of the most popular movies of the past four decades, to all intents and purposes Sir Alec simply declines to discuss them. He does not tell how he played eight different parts in "Kind Hearts and Coronets," or what varieties of discomfort and inconvenience he suffered while making "The Bridge on the River Kwai," or how he managed to transform himself into the heroically irascible Gulley Jimson in "The Horse's Mouth." He has, quite simply, other fish to fry, and little time or space for cinematic gossip.

No doubt this will come as a disappointment to many readers, who will assume -- not without just cause -- that when a famous actor sits down to write his life's story he will tell them anecdotes from his career in films. What these readers forget, though, is that writing a memoir is not merely a matter of telling one's story from Point A to Point B and making all the local stops along the way. As much as any other form of writing, a memoir involves selection and discrimination. For reasons of space as well as discretion and reticence, not everything can be told; the memoirist therefore must decide what he will and will not tell, and in so doing makes crucial decisions about what is and is not important in his life -- about what really matters to him, and about what he thinks will be most interesting and instructive to his readers.

If anything, it is remarkable how many different causes the memoir can be made to serve. Consider "The Autobiography of Benjamin Franklin." It is an American classic, though there is ample reason to characterize it as a work of fiction; it is less an autobiography than an artful fabrication. The Franklin who emerges in its pages is not the real man as seen by his contemporaries and as revealed in many of his other writings, but a carefully contrived idealization of that real man: The autobiography gives us the legendary Franklin who was early to bed and early to rise, not the actual Franklin who kissed the girls and made them cry. What Franklin wanted to do was locate himself in American history and provide a model for youths to emulate; in the memoir, he found a convenient way to do so -- just as, in "The Education of Henry Adams," its author found a convenient form for elucidating his private and somewhat eccentric theories of history.

Crossing that thin and sometimes invisible line between fact and fiction is common among memoirists. The first and most obvious explanation is that even the most retentive memory is selective and suspect; more to the point is that the memoir is yet another kind of storytelling, and in order to tell a good story it is usually necessary to rearrange, revise and, should the occasion arise, invent. One of the best autobiographies of recent vintage, Frank Conroy's "Stop-Time," is constructed much like a novel; since many of the stories in Conroy's recent collection, "Midair," are constructed much like autobiography, it is easy to conclude that in important respects Conroy is a writer of fiction working within the framework of the memoir.

James Thurber's "My Life and Hard Times" and H.L. Mencken's "Happy Days," two of the best and funniest American memoirs, cross the line constantly, though it is quite impossible to tell where the crossings occur. Thurber's classic chapter about the night the bed fell on his father is constructed as artfully as the most accomplished short story, containing effects both dramatic and humorous that clearly are arranged to suit the author's convenience; Mencken warns the reader that "I have made a reasonably honest effort to stick to the cardinal facts, however disgraceful to either the quick or the dead, but no one is better aware than I am of the fallibility of human recollection." Combine that fallibility with the memoirist's desire to entertain and instruct, and you have something that isn't exactly fiction, but most certainly isn't fact -- though it may come a lot closer to the truth than a mere recitation of the facts ever could.

Often the memoirist is not even his own main subject. Clarence Day's "Life With Father," Geoffrey Wolff's "The Duke of Deception," Hilary Masters' "Last Stands" -- all are memoirs in form and spirit, yet all really are about the authors' fathers. Eileen Simpson's "Poets in Their Youth" and Joyce Johnson's "Minor Characters" certainly are memoirs, but more importantly they are recollections of literary figures both major and minor with whom the authors were intimate; both authors are trying -- with notable success -- not to dazzle us with famous persons they have met, but to remember what it was like when they and those famous persons were young, to help us understand the circumstances in which their fame was forged.

What all of these books have in common is not merely that they are memoirs but that their authors are attempting to draw serious and meaningful conclusions from their own experiences. Willie Morris' "North Toward Home" is distinguished by its author's considerable gifts as a raconteur but also by his effort to locate within his own life the connections and disconnections between North and South. Similarly, Anthony Bailey's "America Lost & Found" is a charming story of a British boy living in America during World War II, but at a deeper level it is an inquiry into cultural differences and the ways in which we seek to bridge them.

All of which is to say that although a memoir is a document to which the reader brings a particular set of expectations, we must always bear in mind that it is the writer, not the reader, who is in control. We may be pleased or disappointed by the choices the memoirist makes, but they are choices dictated by that person's desire to find sense and meaning in his life -- to tell us, in effect, what did and did not matter. In "Blessings in Disguise" Sir Alec Guinness says that filming movies meant less than the people he came to know and love -- and that, in turn, tells us something about him. Something perhaps approximating the truth.