There must be a tacit understanding, a pact, between an auto biographer and reader that the truth is being told. Such a pact is, I would guess, rarely observed to the full. There are many reasons why the writer should lapse. There may be actions or thoughts which he feels it is simply too shameful to make public. There may be things he decides against putting down on paper because (as he rationalises) they are not important enough. There are also more complex and interesting reasons for surreptitiously breaking the pact.

The autobiographer may decide that the ultimate goal of the work, the truth about himself, can be served by inventing stories that encapsulate the truth more neatly, more pointedly, than strict adherence to the facts ever could. Or he may break the pact by deciding, from the beginning, never to adhere to it. He may call his book an autobiography simply in order to create a positive balance of credulity in the reader's mind that will be extremely convenient for him in his storytelling, and which, in the case of his more naive readers, may not be exhausted even by the time the story ends, so that these readers will go away thinking they have read a true history, when they have read nothing but a fiction. All of which can be clone in no particular spirit of cynicism.