The concept of memory has evolved significantly, shifting from spatial models to the idea of mental time travel (MTT). This article delves into the intricacies of MTT to the past, comparing it with physical time travel (TT) to better understand its nature and limitations, particularly focusing on answering “Can Consciousness Travel Back In Time?”. While TT remains a theoretical concept, its established characteristics offer valuable insights into the phenomenal and metaphysical aspects of MTT.
Introduction: The Rise of Mental Time Travel
Spatial models once dominated memory research. However, the mental time travel metaphor gained traction around 1980, shifting focus from spatial memory to its temporal dimension. Endel Tulving, a pioneer in this field, described MTT as the ability to mentally roam through one’s past and future, independent of physical laws. This perspective reframed memory, emphasizing the subjective experience of remembering over internal processes. This shift, prioritizing temporality and consciousness, led to new research approaches and philosophical theories like the simulation theory of memory.
Despite MTT’s influence, its meaning and adequacy remain debated. This article aims for a focused objective: understanding time travel to the past within the mind. Drawing parallels with the extensively discussed concept of physical time travel, it explores how memories can be considered a form of mental TT.
This analysis focuses on TT and MTT to the past for three main reasons: to understand memory metaphors’ influence on scientific research, particularly regarding imagination and memory; to comprehend the MTT metaphor within its primary context of explaining memory, and because MTT to the past may differ significantly from MTT to the future. This paper offers a detailed analysis of MTT’s unique characteristics through comparison with TT, examining both similarities and differences and shedding light on the phenomenal and metaphysical aspects of MTT to the past.
A General Overview of Time Travel
The concept of time travel gained popularity in the late 19th century with H.G. Wells’ “Time Machine”. Before then, the prevalence of presentism (the belief that only the present is real) hindered the consideration of TT. However, with the emergence of relativity theory, alternative conceptions of time gained traction. By the late 1970s, TT became a subject of philosophical inquiry, notably with David Lewis’ “The Paradoxes of Time Travel.”
While TT remains hypothetical, philosophers and physicists debate its logical and physical possibility. Despite varying conceptualizations, general characterizations of TT exist within orthodox theories of time.
Here are key characteristics of time travel to the past:
- A temporal destination distinct from the present.
- A distinction between subjective and objective time.
- The traveler’s experience of the past.
- The distinction between the traveler and their past self.
- The existence of the past.
- The unchangeability of the past.
The following sections will examine each of these characteristics and draw parallels with MTT to the past.
Traveling to a Temporal Destination Different from the Present
Time travel typically involves removing a traveler from the normal flow of time, resulting in their appearance at an earlier or later point. The destination involves a change from one point in time to another. Time travel can be intentional or unintentional, and the time traveler can become aware of his temporal displacement upon arrival.
Mental time travel, a mental travel occurring in subjective time, should also exhibit this essential characteristic. The individual needs to experience, if not going, at least arriving at a time different than the present. Several factors contribute to the vividness and the sense of reliving the past. For example, visual imagery, emotional processes, and self-referential thinking. For instance, revisiting a location can trigger memories and mentally transport individuals back to specific points in their past. Even conversations can play a role in an embodied MTT experience where an individual reenacts movements associated with past experiences. Involuntary memories and MTTs to the past are also highly common. For example, those associated with post-traumatic stress disorder (PTSD) can exemplify instances where the time traveler neither chooses to engage in time travel, nor realizes (for a short period of time) that they have actually traveled through time.
While some memories may not fully align with MTT, the analysis focuses on memories that, at a minimum, adhere to this essential condition that captures the conscious experience and phenomenal aspects of certain memories of personal past experiences.
However, there are some important differences that set mental time travel apart from the standard idea of time travel. First, MTT is bound to an individual’s personal history. The individual cannot journey to a time prior to their existence. Secondly, while the destinations of TT are precise spatio-temporal coordinates, most of our memories do not have this characteristic. The individual memory may not refer to experience-near events, they involve abstracted, summarized, and generalized events that span extended periods. Finally, the destinations of our MTTs are not typically stable and punctual; they fluctuate between simple and more complex, abstract events.
Difference Between the Personal Time of the Time Traveler and the External Time
A defining feature of TT is the divergence between personal and external time, where the time experienced by the traveler differs from the objective time. This is illustrated by the time gap between departure and arrival. In MTT, there should also be a distinction between the personal time of the traveler and the external time. This discrepancy is noticeable in many acts of recollection. Mental time travel is evident in various interpretations of the characteristic attributed to TT.
The distinction between subjective time and objective time in MTT is evident, as is its rapid occurrence, and that it entails no discernible cognitive cost for the traveler. Furthermore, mental time travel exhibits scale-invariance, meaning the rate of event production, or the speed of access to the past event, remains constant across different timescales, whether recalling recent activities, events from the past week, or even events from years ago. The key point is that the subjective time and the external time differ.
Experiencing and Re-Experiencing the Past
There has been limited exploration of the conscious experience itself of TT for the time traveler. By employing conceptual analysis, one can speculate on the different forms of conscious experiences based on potential destinations in a block-universe.
There are three distinct types of conscious experiences that the time traveler can undergo: (a) a completely new experience, (b) a complete re-experience, but from a third-person (visual) perspective, and (c) a mixed experience where some aspects are re-experienced from a third-person (visual) perspective while others are experienced as new. Instances where time travelers travel to a time when they were alive and had first hand experience, yet do not remember it, also result in a new experience for the traveler. All these experiences come with a feeling of presence, given that the past is physically present, both temporally and spatially. At the same time, a feeling of pastness can be also part of the experience, especially in (b) cases, where what is present is experienced as some events that already took place in our personal past.
Cases falling under category (a) appear to be incompatible with MTT, particularly those that do not exhibit even a minimal sense of pastness. On the other hand, cases falling under category (b) represent the most commonly observed phenomenology associated with MTT in the literature.
The presences of vivid visual imagery, affective and emotional processes, and self-referential processes all play a role in determining the feeling of re-experience. Other factors are also at play, however, such as auditory cues, odor cues, contextual cues, and material factors, are also likely to have a significant impact on generating and intensifying the feeling of re-experiencing.
While a complete re-experience is commonly associated with mental time travel, there is a crucial distinction between the re-experience in TT and MTT. In TT, the past is always relived from a third-person visual perspective, whereas in MTT, the visual perspective can also be from a first-person point of view. Finally, while a completely new experience is if not possible at least highly unlikely in MTT, a mixed-experience where certain aspects are re-experienced while others are experienced for the first time is indeed, in certain ways, more plausible.
The Traveler and the Past Self
In general, philosophers acknowledge the possibility of traveling back in time to a period in which one’s earlier self-existed. Regardless of the theory of persistence through time adopted, it is necessary to recognize that the time traveler and the past self-differ in at least some properties and can always be distinguishable despite being the same person. Also, the conscious experience of the time traveler has not been discussed in philosophical literature, but some more or less plausible hypotheses can be proposed. From a visuospatial standpoint, it is likely that the traveler adopts a third person perspective.
MTT lends itself more naturally to a first-person perspective, where the mental time traveler relives their past self and assumes their previous perspective by mentally traveling back in time, thereby re-experiencing their past emotions and evaluations. These instances of “fusion” between the past and present self, possible in MTT, represent a notable distinction compared to TT, where such fusion does not seem likely. Despite being less compatible with the association commonly found in the literature between MTT and reliving past experiences, the evaluative and affective third-person perspective can, in principle, also exist in MTT. Indeed, empirical research provides support for these philosophical viewpoints. The erasure of the first-person perspective and its substitution with a third-person perspective, which can result in either a more accurate or more distorted recollection of the memory, is a unique feature of MTT and cannot occur in TT. The malleability of mental time also accounts for the diversity of perspectives that can be adopted in MTT, a phenomenon that is more commonly associated with the realm of the mind compared to TT.
The Existence of the Past
In order to travel through time, there must be distinct temporal parts or stages, situated at various times and places, that exhibit changes between them. The intended destination must have actual existence as a physical location in the space–time manifold. In MTT, it should also be necessary for the past to have some form of existence in order to travel there, though not necessarily a physical existence in the space–time manifold.
Involuntary memories, particularly those related to trauma and PTSD, serve as powerful agents that bring the past alive and give it a feeling of existence. Memories that arise through the technique of “context reinstatement” are likely a better illustration of memories that can potentially evoke a sense of traveling back to an existing past. It can be asserted that in certain cases of MTT, the past possesses not only a mental existence but also a physical one—albeit not as a location within the four-dimensional manifold of space–time, as in TT. Nevertheless, exograms and material traces are not always necessary to enable the emergence of the mental past.
The notion that the mental existence of the past in MTT must ultimately rely on some form of physical existence, such as memory traces in the brain, appears to be unfounded. In conclusion, whereas in TT the existence of the past is contingent upon its physical manifestation, MTT allows for a past that does not require physical existence.
A Changing or Unchanged Past
It is widely accepted that only a block-universe framework aligns solely with TT, where every event exists in a fixed and unchangeable state. Unlike TT, where changes to the past are considered a highly improbable possibility, MTT operates on the premise that changes to the past are the norm.
First and foremost, memories are not literal snapshots of experience preserved in a perceptual form. Changes in condensation and summarization are inherent in every memory and consequently in every instance of MTT.
Secondly, there are other types of changes that certain memories can undergo without necessarily becoming false.
Unlike TT, where changes to the past are considered a highly improbable possibility, MTT operates on the premise that changes to the past are the norm.
When knowledge, concepts, values and morals change, not only can our memories of the past change, but the past events themselves can be altered, as past human events extend beyond mere physical occurrences. Through the faculty of memory (and additionally, by means of historical research), present-day knowledge, concepts, values and morals shape and determine past human actions and events, either by changing the past itself or by resetting reality and giving rise to a new version of that past. There also a third form of change or reality-reset, somewhat distinct from the previous cases, wherein certain memories can undergo alterations without necessarily becoming false. Certain feelings a person experiences may be too vague when they are fully immersed in the experience itself to take a definite shape and be conceptualized and recognized as, for example, anger during the actual experience.
Conclusion
The memory metaphor of MTT has a significant impact on scientific research, prompting us to conceptualize memory as a form of TT that happens in the mind. From a metaphysical perspective, MTT exhibits greater flexibility and malleability compared to TT. The mental nature of time travel in MTT fundamentally alters its essence, emphasizing the importance of understanding its true aspect to assess its relevance in explaining memory. While MTT and TT to the past share some common aspects, notable distinctions exist. My exploration has illuminated the intriguing realm of MTT to the past, revealing its distinctive attributes and encouraging further investigations into the intricacies of this fascinating memory metaphor. By characterizing the key differences and similarities between physical and mental time travel, we can improve our understanding of whether “can consciousness travel back in time”.
