From the French memoirĂ© (memory), a memoir is supposedly a construct of the author’s memories and therefore a work of non-fiction. The thing is, our brains are not computers. We forget, transform, dilute, minimize, exaggerate and mutate memories. Therefore, what the author tells in a memoir might not be exactly what happened. Also, authors may choose to give different contexts for happenings, resulting in different results for the reader. Shield agrees with this, saying that “you’re obligated to use accurate details, but selection is as important a process as imagination.” (pg 30)
Furthermore, an author sometimes chooses to lie in a memoir, believing it will produce a desired effect in the reader.

One of the examples of inexact memoirs that shield gives is that of Thomas De Quinceys Confessions of an English Opium Eater, in which the author speaks of his addiction to Laudanum, an especially potent herbal alcoholic mixture containing all the opium alkaloids. Beginning the first part of his book by stating "I here present you, courteous reader, with the record of a remarkable period in my life....", and by making other similar statements, De Quincey leads the reader to think that he is no longer addicted to Opium, or at least that the most extreme phase of the addiction, that which he recounts in The Pains of Opium, has been overcome. The truth, as revealed by shields, is that “he was taking opium when he wrote the book and continued to take it for the next thirty years”.
There are other things that I believe De Quincey might have altered in his book. His situation of extreme poverty to the point of deadly starvation in the company of a prostitute seems unrealistic since the only thing that De Quincey had to do to escape his situation was to make peace with his guardians and the people in his old life. Although it is true that he had suffered some abuse from their part, starving to death because he would not take a handout seems dramatized.
De Quincy probably altered the truth of his story in an attempt to make his book more instructive. To teach readers about the power and dangers of opium, but also to give addicts hope of recovery. Also, De Quincey probably wanted to enjoy merit from having overcome his addiction.
Shield would probably say that what De Quincey did in his book is perfectly appropriate, because what matters for him are not experiences, but what they made you see. It doesn’t matter who you are, but what you want to say. Shield clearly expresses this view by saying that he thinks “it’s a misunderstanding to read a memoir as though the reader owes the reader the same record of literal accuracy that is owed in newspaper reporting. … What the memoirist owes the reader is the ability to persuade him or her that the narrator is trying, as honestly as possible, to get to the bottom of the experience at hand.”