In this blog post, I’ll explore the philosophical question of whether sharing the same memories makes two people the same person, focusing on the relationship between memory and self-identity.
Someone tells you that you were their first love. If you’ve seen the movie ‘Introduction to Architecture’, you’ve probably felt a sense of nostalgia as you recalled memories of your own first love. But what if the first love you remember is actually a fiction? If you were to discover that your first love never actually existed, and that what you remember is a memory manipulated and implanted by someone else, you would be plunged into an overwhelming sense of emptiness in that very moment. If not only the memory of your first love but everything you know were a fabrication, you might even reach a point where you lose your very sense of self.
The future society depicted in the movie ‘Ghost in the Shell’ illustrates these questions even more dramatically. In the future society depicted in the film, most of people’s bodies are made up of machines, and their brains have been replaced by electronic brains connected to various networks. Consequently, it is possible to manipulate memories by injecting or extracting information from the brain. Outwardly, they do not differ significantly from humans today; they are capable of independent thought and can maintain basic life functions. Furthermore, the concept of the “Ghost”—what we commonly refer to as the soul—emerges as a key element in the story.
In this society of extreme technological advancement, the cyborgs Bat and Major Kusanagi question whether they died long ago and whether their current selves are merely simulated personalities composed of electronic brains and cyberbodies. This stems from the idea that the vast memories and information a human possesses are ultimately part of themselves and that this is what forms their self. According to this logic, if the memories I currently possess could be transferred or stored exactly as they are into another being, it follows that my sense of self could also be reproduced exactly as it is. But if only the same memories exist, can the same sense of self truly be formed?
Let’s limit the definition of “memory” here to the act of retaining past impressions or experiences in one’s consciousness or recalling them. The key point to note here is that the very process of storing the same event as a memory is highly subjective. This is known as the Rashomon Effect: due to the subjectivity of memory, people remember the same event in different ways even when they have experienced it identically. As information received from the external environment passes through the senses and is stored in the brain, details deemed unimportant are selectively filtered out. In this process, memories can naturally become distorted. Subsequently, when recalling past memories, it is not uncommon for people to believe these distorted details to be actual facts. Ultimately, because the criteria for judging what is important and what is not differ from person to person, memories are also formed differently for each individual.
In other words, these subjective differences can be attributed to differences in the criteria used to store memories. These criteria can be broadly divided into two factors: knowledge and experience accumulated over a long period of time, and personal preferences and emotions.
First, knowledge and experience accumulated over a long period of time are the result of previously formed memories. Events that actually occurred in the past are stored as memories after passing through an individual’s subjective interpretation, and these memories subsequently serve as criteria for judging new situations. While these memories have the greatest influence on interpreting situations similar to current experiences, they can also affect situations that are not directly related. Furthermore, they are a major cause of what people commonly refer to as “prejudice.”
Next, an individual’s preferences and emotions also have a significant influence on memory formation. This is because humans are not purely rational beings. Even when experiencing the same situation, the memory retained can be completely different depending on one’s emotional state at the time. For example, when a cup is half-full of water, one person might interpret it positively as “half the water is left,” while another might interpret it negatively as “only half the water is left.” Such differences play a significant role not only in the process of forming memories but also in the process of constructing one’s self.
Based on this fact, let’s assume that my memories are stored exactly as they are on a specific computer. Could a computer with the exact same sense of self as mine then be created? I believe the answer is no, for two main reasons.
The first reason is that memory—a key element in the construction of the self—is constantly changing over time. Memories gradually fade, and they are continually revised as new experiences are reinterpreted according to existing subjective standards. For example, suppose I drew a picture on a sandy beach. Even if someone were to copy that drawing perfectly, over time the waves would cause the two images to gradually differ in shape. Before long, it would be difficult to say that the two drawings are exactly the same. The same applies to memory. Even if my memory were perfectly replicated at a single moment, from that point onward, as new experiences accumulate in different ways, my memory would inevitably change. This is because, even if only a few seconds pass, the situations each person experiences and the ways they interpret them differ from one another.
The second reason is that an individual’s preferences and inclinations cannot be completely replaced by memory alone. For example, even if my memories were transferred exactly as they are to another person, that person’s original inclinations and preferences would not become completely identical to mine. Although they might experience some confusion at first due to the influence of those memories, it is highly likely that, over time, they will reform their sense of self based on their original dispositions and values. Ultimately, not only memories but also an individual’s enduring dispositions and values play a crucial role in shaping the self.
Ultimately, the reason I can be myself is that it is nearly impossible to maintain not only my memories but also my personal preferences and dispositions consistently unchanged. Memories are constantly changing, and an individual’s values and dispositions are also continually shaped and refined through new experiences. Although artificial intelligence, neuroscience, and brain-computer interface technologies are advancing rapidly today, at the current stage of research, it has not yet been possible to completely replicate or transfer human memory and the self. Therefore, it is difficult to conclude that having the same memories necessarily makes two people the same person. Rather, the self can be described as a complex result shaped not only by memory but also by ongoing experiences, values, and dispositions.
