Good faithHuman memory is a marvellous but fallacious instrument. This is a threadbare truth known not only to psychologists but also to anyone who has paid attention to the behaviour of those who surround him, or even to his own bahviour. The memories which lie within us are not carved in stone; not only do they tend to become erased as the years go by, but often they change, or even increase by incorporating extraneous features. Judges know this very well: it almost never happens that two eyewitnesses of the same event describe it in the same way and with the same words, even if the event is recent and neither of them has a personal interest in distorting it. This scant reliability of our memory will be satisfactorily explained only when we know in what language, in what alphabet they are written, on what material, and with what pen: to this day we are still far from this goal. Some mechanisms are known which falsify memory under particular conditions: traumas, not only cerebral ones; interference by other 'competitive' memories; abnormal conditions of consciousness; repressions; blockages. Nevertheless, even under normal conditions a slow degradation is at work, an obfuscation of outlines, a, so-to-speak, psychological oblivion, which few memories resist. It is probable that one may recognise here one of the great powers of nature, the same that degrades order into disorder, youth into old age, and extinguishes life in death. It is certain that practice (in this case, frequent re-evocation) keeps memories fresh and alive in the same manner in which a muscle that is often used remains efficient; but it is also true that a memory evoked too often, and expressed in the form of a story, tends to become fixed in a stereotype, in a form tested by experience, crystallised, perfected, adorned, which installs itself in the place of the raw memory and grows at its expense.
Now, anyone who has sufficient experience of human affairs knows that the distinction (the opposition, a linguist would say) good faith/bad faith is optimistic and illuminist, and is all the more so, and for much greater reason, when applied to men such as those just mentioned. It presupposes a mental clarity which few have, and which even these few immediately lose when, for whatever reason, past or present reality arouses anxiety or discomfort in them. Under such conditions there are, it is true, those who lie consciously, coldly falsifying reality itself, but more numerous are those who weigh anchor, move off, momentarily or forever, from genuine memories, and fabricate for themselves a convenient reality. The past is a burden to them; they feel repugnance for the things done or suffered, and tend to replace them with others. The substitution may begin in full awareness, with an invented scenario, mendacious, restored, but less painful than the real one; in repeating its description to others but also to themselves, the distinction between true and false progressively loses its contours, and man ends by fully believing the story he has told so many times and still continues to tell, polishing and retouching here and there the details which are least credible or incongruous or incompatible with the acquired picture of historically accepted events: initial bad faith has become good faith. The silent transition from falsehood to self-deception is useful: anyone who lies in good faith is better off, he recites his part better, is more easily believed by the judge, the historian, the reader, his wife and his children.
......I can recognise in him the typical case of someone who, accustomed to lying publicly, ends by lying in private too, to himself, and building for himself a comforting truth which allows him to live in peace. To keep good faith and bad faith distinct costs a lot: it requires a decent sincerity or truthfulness with oneself, it demands a continuous intellectual and moral effort.
Primo Levi, The Drowned and the Saved, pp.11-5