Memory is defined as the store of things learned and retained from an organism’s activity or experience as evidenced by modification of structure or behavior or by recall and recognition. The relationship between memory and personal identity has been explored by both scientists and philosophers for centuries. From Descartes to John Locke, David Hume and H.P. Grice, definitions of personal identity have been linked to the mind, consciousness, memory, and changing perceptions. The notion that memory is a crucial aspect of one’s personal identity has been assumed, and the diversity in the perception of experiences held by each person has been acknowledged. However, the philosophers’ various interpretations of the memory theory that ties to personal identity lead us to grapple with a few fundamental questions: Who are we? How closely can identity be tied to a changing variable? If we assume memories to be potentially unreliable, as they ultimately depend on recall and recognition which are easily influenced by new experiences and subsequent memory storage, the integrity of identity comes into question. And, if our memory fails, either as a result of the passage of time or due to illness, have we only lost the database of past experiences from which new memories are created, or have we also lost crucial elements of our personal identity? Memories, although often times unreliable, serve as the foundation of one’s personal identity. The brain constantly analyzes new experiences, makes connections with similar past experiences, and forms connections. When a person undergoes a new experience, one neuron in his brain activates another neuron by firing an action potential. This signal is captured by the second neuron in a space between the two cells called the synapse. A memory is created when this signal is repeatedly delivered over a period of time. A concept known as synaptic plasticity describes the ability of synapses to become either stronger or weaker as a result of increased or decreased use over time; if the synapse is utilized more often, it becomes stronger. Therefore, the likelihood of creating a memory increases with the frequency of action potentials and communication between two specific neurons. Furthermore, the process of storing long term and short term memories is different. Every memory, when first experienced, is initially considered a short term memory, and travels through the prefrontal lobe in the brain. The prefrontal lobe only stores this information for a few minutes before it is “thrown out.” However, if the signal is continuous, the brain recognizes it as a long term memory, and the information becomes encoded in the hippocampus. Therefore, when short term experiences are frequently processed in the prefrontal lobe, the likelihood of information transmittance and retention in the hippocampus increases.Memories allow us to extract impressions of past perceptions. Every experience, and thus memory, has multiple features that are stored independently of each other. For example, when a boy attends a major league baseball game, he encounters different emotions during the game, smells of the stadium, noise in the stadium, and the sight of the game. These various elements consolidate to form one complete memory; however, because these characteristics are not stored collectively, each one can be recalled separately. This allows the initial memory to resurface when an unrelated experience evokes an emotion similar to that felt during the game. This idea is reflected in the results of a study conducted at UCLA, which demonstrated that memories never occur in isolation. That is, the formation of new memories is heavily influenced by comparable past experiences in a process known as maturing. In maturing, the brain draws information from similar past experiences to provide itself with enhanced coping mechanisms for the present. It is not uncommon, however, for individuals to forget significant past experiences, therefore disabling them from referring to these experiences during the process of interpreting present stimuli. Consider John, who was grounded for a week after yelling at his neighbors. In the days after being released from his house arrest, John took great precautions around his neighbors, because he remembered the negative consequences that resulted from his previous behavior. It is possible that as time passes, John may forget about the house arrest, which would prevent his brain from drawing an association between his neighbors and cautionary measures. His neighbors’ actions, then, may anger him and cause him to get grounded again. The passage of time caused John to forget his initial punishment, ultimately leading to his second detention. Incidences such as these make it clear that time plays a crucial role in the creation, storage, and recall of memories. While memory is described as the recollection of the past, the brain continuously and simultaneously alters and deletes existing information. Hence, one’s memory, and in consequence, one’s past, can be extremely unreliable. First, memory is a neural network in one’s brain that has the potential to become defective. This defect occurs when a postsynaptic neuron, which normally receives and encodes the action potential, fails to recognize the presynaptic neuron’s signal. As a result, the information is unsuccessfully transmitted and a connection is not made. Second, even memories that are successfully stored undergo constant change, which can lead to slight inaccuracies when that memory is recollected. The neural networks in one’s brain transform to create the new, modified memory. Maureen Murdock, the author of the book Unreliable Truth, explains this concept: “Memory is rarely whole or factually correct. If the image of the event we have participated in does not match the image of the self we have carefully constructed, then we rarely remember the facts of the event at all. What we remember is a reconstruction of image and feeling that suits our needs and purposes.” Murdock’s explanation introduces the concept of personal identity and its dependence on memory. John Locke, who was a student and critic of Descartes’ philosophies of rationalism and of mind-body dualism, believes that the mind is isolated from the body. He feels that the “thinking substance” (the brain) is not equivalent to the consciousness (memory or mind); rather, it is personal identity that is tied to consciousness. In fact, as an empiricist, Locke proposes that personal identity is shaped by one’s experiences and reflections. This differs from the Cartesian theory of “innate certain knowledge,” which argues that people are born with basic tenets of knowledge. Locke instead describes a “tabula rasa”, or blank slate, upon which our experiences write. However, in its extreme, Locke’s idea is that memory is a necessary condition of personal identity, and that an individual’s identity may only extend to the reaches of that person’s consciousness. Furthermore, if one cannot remember having a particular experience, one did not have the experience. And if we remember perceptions inaccurately, it puts our identity into question. H.P. Grice addresses some of the concerns held by later philosophers regarding the rigidity of Locke’s ideas. He argues that the inability to remember an experience does not indicate the absence of that experience. Grice, instead, introduces the concept of the total temporary state, which is composed of all the experiences any person has at a given time, providing a link of continuity between them. It can be said, then, that personal identities are composed of a series of total temporary states. For example, if a teenager recalls a childhood experience of a stepping on a nail, he remembers to wear hard-soled shoes when he leaves his home. As an older man, he may not remember the nail-in-the-foot experience, but he does remember to wear hard-soled shoes for stability when he walks. Thus, if a memory of a childhood event is lost by the older man, the transitive property applies; if the older man recalls his teenage experiences, and the teenager recalls the childhood experiences, the personal identity is retained as a continuity of history and, therefore, remains intact. This is a further representation of how time affects both the recollection and storage of memories. In David Hume’s “A Treatise of Human Nature,” he describes the “true idea of the human mind…as a system of different perceptions or different existences, which are link’d together by the relation of cause and effect.” Hume defines three elements on which identity depends: resemblance, contiguity, and causation. In effect, these individual elements and their relationship to one another allow for a relationship of cause and effect among our perceptions. Hume also introduces the concept that these causal relationships make memory possible by stating that “the same person may vary his character and disposition, as well as his impressions and ideas, without losing his identity…his several parts are still connected by the relation of causation.” So, even if small alterations exist in the composition of the whole, the different parts remain connected by the relation of causation, allowing for the preservation of the identity.Thus far, the interconnection between changing memories and identity has been elucidated. Nevertheless, the effect that disease-induced memory loss has on consciousness and identity must also be explored. This concept was first addressed by Hume in his Treatise, “Had we no memory, we never should have any notion of causation, nor consequently of that chain of causes and effects, which constitute our self or person.” Two hundred and seventy-nine years after its publication, the same question is asked: since memory contributes to defining our identity, does memory loss change who we are? It is estimated that, globally, fourteen percent of people will develop some form of dementia, with ten percent of the world developing Alzheimer’s disease. Interestingly, it has been shown that people with memory-loss first demonstrate symptoms of their disease in the form of personality and behavior changes. This includes a loss of interest in previously enjoyed activities, social withdrawal, and isolation. Sometimes these changes in character are so extreme that the person becomes unrecognizable to his or her family and closest friends. In addition, past experiences may be forgotten, and memories of who he once was and of the experiences that shaped him are lost. These individuals have essentially come full circle by returning to Locke’s tabula rasa. Overall, the philosophers studied would agree that a person without memory also loses his identity. After reading and analyzing numerous philosophers’ ideas, I will provide my perspective on the initial, core questions. First, who are we? I agree with the concept that memories are integral in the creation of personal identity. One’s character, behavior, and decision making process are constructed by a collection of past experiences. This compilation not only shapes how we remember our past, but also influences our interpretation of current events and future outlook. Each individual has a diverse set of memories that makes him unique as compared to his peers; an experience that one person interprets as positive may be deemed dubious by another. Our memory of various situations allows us to learn from mistakes, try to repeat past successes, and make decisions based on previous experiences’ outcomes. How closely can identity be tied to a changing variable? Our memory is prone to an imperfect recollection of past events due to both the passage of time and the addition of subsequent experiences that color the initial one. The fact that our identities are grounded by a variable that is so modifiable should actually be seen as favorable. While the studied philosophers do not explicitly state that memory’s capacity to adapt is negative, they fail to recognize its advantages. Change in a person by way of his memory represents growth and maturation, which is necessary for improvement and success. If an individual does not encounter altered versions of his memories, he is stripped of the opportunity to expand beyond his initial perspective. If a childhood memory, for example, is unaffected by time and successive experiences, the current mindset will remain consistent with what already exists. This is problematic, as change is essential for the development of a person’s character. It is clear, then, that time provides us with the freedom to progress. What happens to our identity if our memory dissolves, either as a result of the passage of time or a disease? Once again, I agree with the notion that a person no longer holds his identity without his memory. How can somebody be himself if he doesn’t even know who he is? This absence of self is seen in individuals who suffer from memory loss illnesses such as dementia. My grandmother, who was a victim of Alzheimer’s disease, recently passed away. Although December 6th, 2016 marks the date of her physical death, she essentially died with no memory, the loss of which occurred years before. What started as forgetfulness and inaccurate recollections of our shared experiences quickly advanced to losing any memory of her parents, husband, and children. Not only did she blankly stare at me when I entered her home, but I, too, was desperate to recognize the Grandma I knew and loved. Her defining personality traits expired with her memory – she no longer enjoyed eating mozzarella and prosciutto, her two favorite foods, and when I put the Nets’ basketball game on the television, her favorite sport, she turned away. Dementia successfully stole my grandmother’s memory, making it impossible for her, and other individuals like her, to maintain her identity. Memory is an essential, foundational element of one’s identity. While memories are used to construct perceptions of past, present, and future events, they also have the capacity to adapt to change. This change manifests in various ways: incorrect recollection, additional experiences integrating into previous ones, and memory loss diseases. For many years, philosophers have argued that time’s ability to alter a memory contributes to the development of one’s identity. They believe that a person’s identity is completely dependent on the collection of memories made throughout his life. Therefore, the logic supporting the argument that memories form personal identity is valid. One may present the counter-argument, which parallels the innate knowledge theory, that someone is instead born with a predisposition to his or her possessed characteristics. While this statement may be true for a person’s physical traits, identity is ultimately defined by the effect that the introduction of new experiences, the passage of time, and brain alterations have on memory. It would be interesting to conduct further research into this subject to gain a deeper understanding of the relationship between memory, identity, and time. One potential study could be to investigate patients with head injuries that are amnestic. This would entail communication with the patients’ close relatives to learn about their personalities both before and following the injury, and determining whether their goals, preferences and aversions have changed. We would discover, then, whether we are are creatures with Cartesian innate knowledge, or rather are Locke’s blank slates that, in time, are filled.