"Logical and Philosophical Issues of Time Travel and Science Fiction," by Tim Van Dyke

Stories of traveling through time have long fascinated the science fiction realm. By stimulating our imaginations and curiosity with amazing technology, and challenging our logic with mind bending paradoxes and alternate realities, it is no wonder that such stories continue to be a popular box office showing. The stories take our minds through the boundaries of space and time, jumping to and fro through alternate universes and looping back through parallel time lines, and with the ever accelerating advancement of technology, it is starting to feel as though these fictional stories of time travel may soon become a reality. However, the very thing that makes these stories so enticing may be the same reason that these stories will forever remain in the category of fiction. Time travel stories challenge logic and reason, but a thorough answering of this challenge often times proves these fantastic stories to be completely illogical.

The majority of the mental battles fought in the ring of time travel are not those concerning the physical workings of the technology used to travel, but rather, the main mental struggle presented by these stories lies in the nature of the particular universe. Different stories use different sets of laws to govern time travel in an attempt to make these stories logical. The majority of time travel stories, both short and long, fall under two main categories; those involving a constant or predetermined time line, and those involving a changeable time line.

The first type of time travel story involves those with changeable time lines. It seems as though many of these stories are meant to entertain the masses with fanciful time travel and often disregard any logical problems that may arise because of this. Unlike a constant time line which is very successful at avoiding such problems, this type of time line often runs into paradoxes that are associated with changing the past. Although many of these stories usually contain an explanation attempting to resolve such problems, more times than not, these are also logically unsound. Perhaps the most popular example of such a time line is that found in the Back to the Future films. Michael J. Fox travels back into time in a modified DeLorean to change the past and, consequently, the subsequent future. The actions of the dynamic duo in the past completely alter the future from which they came, and with the exception of the two who did the time traveling, nobody has any memory of the old time line. This story is unique in that someone actually has a memory of the previous time line. Many stories involving a changeable time line take a less family friendly approach to the issues regarding changing the past by completely eliminating any memory of the original time line after a change has been made. There is no evidence that there has ever been a change in the time line, thus avoiding one particular paradox. In either case, the travelers are changing the past, and when this occurs, the present world from which they originate will no longer exist. Although a world with the same place in time will exist, it will not be the same world. If this change in worlds is substantial enough, the time travelers may not even exist to change the past in the first place, creating a paradox.

Although clever screen writing usually hides any paradoxes that arise, close examination of most films will reveal logical problems. The most popular example of such a problem is what is known as the Grandfather Paradox. In this example a young man has developed a deep hatred for his grandfather and wishes to kill him, but he has already died. He purchases a fully functioning pistol and makes his way to the nearest time machine. With his fully loaded pistol in hand, he travels back through the past to a time before his father was born and before his grandfather had met his grandmother. With complete resolution and absolute accuracy he takes aim at his grandfather, and ... ? The question presented in this example is whether or not the young man is capable of killing his grandfather. If he manages to kill his grandfather then he will never be born which means he is unable to kill his grandfather in the first place. This is a fundamental paradox and a huge logical problem for the possibility of time travel. However, some philosophers argue that examples such as these do not eliminate the possibility of time travel, rather, they only prove that a universe in which time travel is possible must be far different from our own and our current understanding of it. In order for this situation to have ever existed in the first place, some completely unrelated force, however improbable, must intercede and prevent the young man from killing his father. Science fiction stories present various ideas for this force such as, the universe preventing this type of an action through improbable events such as the gun misfiring, the young man being involuntarily hurled back into his original present by the laws of time travel, or an entirely new universe is created when traveling through time, therefore avoiding any paradoxes completely.

The second form of time travel story, an unchangeable time line, is the easier to logically explain. One terrific example of this type of time line is that presented in the film 12 Monkeys. In a post apocalyptic subterranean world, prisoner Bruce Willis “volunteers” to travel back into time to search for information on the group known as the 12 Monkeys which are believed to have released a virus responsible for wiping out most of mankind. In doing this he discovers that the formation of the 12 Monkeys was caused because he was sent back into time, however, he was sent back into time because of the 12 Monkeys. This series of events where the original cause is also the original effect of the same cause is known as a causal loop. It seems as though this loop in the time line has always existed. The time line used in 12 Monkeys is unchangeable, and the events that the time traveler experiences occur in the exact same manner because they have been permanently built into the structure of the time line. Although at first, this concept may be somewhat difficult to understand, it is completely logical, and 12 Monkeys seems to successfully avoid paradoxes through the use of this permanent time line. Other films use different methods of avoiding paradoxes, but in every case the goal is always the same, to prevent a change and ensure consistency in the time line.

However, even if time travel stories completely avoid running into paradoxical problems, they may still encounter a number of philosophical problems. The first and most important of which is whether time truly exists. Upon first glance, such a question seems rather ridiculous. Of course time is real, it is all around us. We seem to feel time as we pass through it, we have created precise mechanical devices to measure it, and many of us, especially in western culture, seek to squeeze every ounce of it for all its worth. Many people will live their entire lives and not give such a notion a seconds thought. However, not long after some thought is put into the nature of time does this idea quickly begin to crumble. St. Augustine prosed “What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not.” All time travel stories rely on the very important assumption that time is or has a dimension(s) that can be traveled through. However, philosophers have been challenging this assumption for centuries and have landed on two major schools of thought: realism and anti-realism. The former of which states that time exists outside of the human mind. Although the functioning and dimensions of time may be largely unknown or beyond human understanding, it has some sort of physical presence in the universe and directly interacts with matter. The latter of these two is fairly self explanatory; anti-realism is the opposite of realism. In this view time does not exist as an entity of the universe but is merely a construct of the mind, a necessary element in understanding our existence. All time travel stories must adhere to realism simply because it is impossible to travel through that which does not exist.

In addition to time having reality in the universe, it must also possess another very fundamental property in order for time travel to be a logical reality. All theoretical times must exist at every moment. This view of the nature of time is known as eternalism. Although we feel as though we are constantly experiencing the present, we are at each moment, simultaneously experiencing every other moment in time that we have ever experienced and will ever experience. Essentially, the past needs to exist in order for it to be a destination and the same holds for the future. The counterpart to eternalism is what is known as presentism. In this viewpoint only the present exists. There is only one reality and time is seen as the ordered identities of this reality. The past and the future are simply ideas of the mind rather than realities and therefore cannot be traveled to, therefore all time travel stories must hold to the ideas of eternalism

Even if a universe exists where time travel is possible, a host of logical problems arise with actually traveling from one point in time to another. As mentioned earlier, time travel needs to operate under the fundamental assumption of eternalism which states that all objects exist at all times independent of what the “present” may be. For example, this means that Timmy the time traveler currently exists at every single point in time which he will live. If Timmy could be viewed from the 4th dimension where the 4th dimension is time, then Timmy would appear to be a long unchanging temporal worm. But if Timmy enters a time machine and is suddenly whisked off to the Jurassic period, he no longer exists in the section of time where he had supposedly been eternally existing. Here the idea of time travel runs into some logical problems. At first it seems as though this problem is easily solved. If Timmy returns to his present at the exact point in time in which he left, then Timmy will never have actually left his time line. However, Timmy spent five days hunting dinosaurs before returning. If Timmy originally existed as a continuous temporal worm in the fourth dimension of time which is never broken, then how is the dinosaur hunting Timmy accounted for? A new section of temporal Timmy worm has been created in the Jurassic period. This does not seem to be too big of an issue so long as one of the basic assumptions of time travel is completely ignored. Again, time travel is dependent on eternalism, but a new eternal temporal worm has just been created. It is impossible to create something that is supposed to be inherently eternal, and there for, under these parameters, it is impossible to travel through time. The second dinosaur hunting Timmy can only logically exist if he has in fact existed the entire time. The original temporal worm of Timmy was never broken by the time travel machine, nor was a new temporal worm created. Rather, the versions of Timmy traveling through time and hunting dinosaurs have always existed, which means that Timmy has effectively done nothing. In this sense, the term “time travel” attributes too much credit to the time traveler. Although Timmy may feel as though he is bending the fabric of space time or traveling through a worm hole, from the perspective of the 4th dimension, nothing will have changed. In reality, he will perform these actions because that is what the time line dictates. Similar to the time line of 12 Monkeys, this means that the time traveling, dinosaur hunting, and every other action that Timmy has ever done, were all simply part of the unchangeable structure of an already established time line. He did not actually choose to do anything. Rather, he is merely acting out a series of temporal snapshots, of which he is only able to view one frame at a time.

Science fiction time travel stories have the ability to run the mind through a gauntlet of logical challenges. Some stories quickly prove to be incredibly illogical, or at the very least, they require a strong imagination. Others may be completely consistent and logical, but because of this, they may drastically reduce the significance of the time travelers’ actions. Whether traveling through time is a logical possibility or not may never be known, but one thing is for certain. Stories of traveling to a long lost past or an advanced future will continue to fascinate for years to come.