Then at last, often after a long interval, some fresh experience recalls the lost memory of the other event and at the same time reveals the source of the dream. We are thus driven to admit that in the dream we knew and remembered something which was beyond the reach of our waking memory. (1.3.2)
Freud was totally intrigued by the fact that our dreaming minds have access to memories that are out of the reach of our waking minds. He devoted his career to developing theories that could explain how some "parts" or "systems" of our minds could be inaccessible to others. In his view, understanding the relationship between memory and dreams would help psychoanalysts develop more effective strategies for treating psychological disorders.
It may happen that a piece of material occurs in the content of a dream which in the waking state we do not recognize as forming a part of our knowledge or experience. We remember, of course, having dreamt the thing in question, but we cannot remember whether or when we experienced it in real life. We are thus left in doubt as to the source which has been drawn upon by the dream and are tempted to believe that dreams have a power of independent production. (1.3.2)
Throughout The Interpretation of Dreams, Freud speaks from his own experience just as often as he speaks from his knowledge of his patients' dreams. In doing so, he invites his readers to examine their own dream-lives as well. With that in mind, what do you make of the experience that Freud is describing here? How often do your dreams contain clear memories? How often do their "dream-materials" seem entirely new?
All the material making up the content of a dream is in some way derived from experience, that is to say, has been reproduced or remembered in the dream—so much at least we may take for granted. (1.3.1)
If it can be taken for granted that dreams are made up of "reproduced or remembered" materials, why does Freud go to the trouble of making this point, anyway?
Chapter 5, Section A
If I examine my own experience on the subject of the origin of the elements included in the content of dream, I must begin with an assertion that in every dream it is possible to find a point of contact with the experiences of the previous day. This view is confirmed by every dream I look into, whether my own or anyone else's. (5.2.1)
For Freud, an intriguing characteristic of dreams is that they always seem to incorporate a very recent memory—an experience from the day before the dream—but they also combine this memory with others from any moment whatsoever in the dreamer's life. As Freud says later in the book: "Dreams can select their material from any part of the dreamer's life, provided only that there is a train of thought linking the experience of the dream-day (the 'recent' impressions) with the earlier ones" (5.2.5).
Chapter 6, Section G
Patients, to whom I explained this at some appropriate moment, used to parody this newly-gained knowledge by declaring that they were ready to look for recollections dating from a time at which they were not yet alive. (6.8.45)
Clearly, Freud had his work cut out for him when it came to convincing his patients that experiences from their infancies and early childhoods were still wreaking havoc on their lives.
It was distressing to me to think that some of the premises which underlay my psychological explanations of the psychoneuroses were bound to excite skepticism and laughter when they were first met with. For instance, I had been driven to assume that impressions from the second year of life, and sometimes even from the first, left a lasting trace on the emotional life of those who were later to fall ill, and that these impressions—though distorted and exaggerated in many ways by the memory—might constitute the first and deepest foundation for hysterical symptoms. (6.8.45)
Lots of people today take it for granted that our experiences in infancy and early childhood shape us for life, but in Freud's day, this concept was still fairly new. Freud felt sure that infantile and early childhood experiences were often at the root of his patients' illnesses, but he also knew that he was asking his contemporaries to make radical changes in the way they understood memory and the past.
Chapter 7, Section A
In the first place, what we remember of a dream and what we exercise our interpretative arts upon has been mutilated by the trustworthiness of our memory, which seems quite especially incapable of retaining a dream and may well have lost precisely the most important parts of its context. (7.2.2)
In the final chapter of the book, Freud addresses a concern that many other thinkers have raised about the possibility of interpreting dreams correctly. The doubts expressed in this passage aren't his; they're doubts that he refutes wholeheartedly. In his view, we needn't be concerned about our dreams being "mutilated" by our untrustworthy memories, because even the distortions that our memories produce are significant to the meaning of the dream.
Chapter 7, Section D
In the unconscious nothing can be brought to an end, nothing is past or forgotten. (7.5.11)
According to Freud, why is it that memories and impressions live on forever in the unconscious? Why don't they fade and disappear like so many other memories and impressions do?
Chapter 7, Section F
And the value of dreams for giving us knowledge of the future? There is of course no question of that. It would be truer to say instead that they give us knowledge of the past. For dreams are derived from the past in every sense. (7.7.18)
As Freud moves toward the conclusion of The Interpretation of Dreams, he reminds his readers once again that dreams can't reveal the future. Instead, he says, they reveal the past. Because dreams bring to light the wishes and desires of our childhoods, they are windows into our earliest selves.
Nevertheless the ancient belief that dreams foretell the future is not wholly devoid of truth. By picturing our wishes as fulfilled, dreams are after all leading us into the future. But this future, which the dreamer pictures as the present, has been moulded by his indestructible wish into a perfect likeness of the past. (7.7.18)
Throughout his career, Freud became fascinated by the idea of recurrence—that is, the fact that many people, for various reasons, find themselves compelled to repeat the same actions and follow the same patterns over and over again throughout their lives. Here at the end of The Interpretation of Dreams, we catch a glimmer of this interest coming through.