The time travel issue is one of the most controversial questions in the field of philosophy because it is based on the discussion of different types of the time, causes and consequences of actions, casual loops, and on analysing the past, the present, and the future as providing a range of possibilities or a range of facts.
It is important to pay attention to the fact that the possibility of the time travel is discussed with references to the consequences of such a journey. In his paper, William Grey is inclined to present a list of the time travel’s consequences which are characterised as intolerable because of their connection with the time travel paradoxes.
Thus, the time travel can lead to the intolerable and even threatening consequences because of influencing the principle of the cause and effect in relation to the past and future, and as a result, the most threatening is the effects of the reverse causation and casual loops associated with the fact of the time travel.
The time travel is possible only with references to the Parmenidean view of reality according to which the past, the present, and the future can exist not only eternally but also during the same time period. From this point, the past, the present, and the future exist at the same moment, and any changes as the result of the time travel are impossible, but the possibility of that fact provokes the discussion of intolerable consequences.
According to Grey, the intolerable consequences of the time travel if it is admitted by the philosopher are the reverse causation, casual loops, the correlation between the personal and external time, and the psychological perspective connected with the time traveller’s perception of his journey and observed anomalous reality (Grey 1994, p. 35).
Grey’s argument is based on the evidence discussed in the article by David Lewis, and it can be considered as rather persuasive because the time travel is analysed as the event which can change the reality even if this reality cannot be changed because of the Parmenidean vision of it.
Thus, the most threatening effects or time travel consequences are expected in relation to the phenomena of the reverse causation and casual loops along with the closed casual chains.
Grey states that sharing the idea of the time travel, it is important to rely on the opinion that the events discussed in relation to the past and future are facts, not possibilities, because “cause and effect both exist, though temporally separated, and … these two existing events stand in the casual relation” (Grey 1994, p. 37).
From this perspective, the reverse causation supports the idea that time travellers cannot change the history because of principles of fatalism as accepting all the events as given facts. Grey claims, “We are all fatalists about the past, but reverse causation extends the same considerations to the future” (Grey 1994, p. 37).
That is why casual loops and the phenomenon of the reverse causation are effective for preventing time travellers from changing the history in relation to the external time. However, the problem is in the fact that time travellers remain to be able to change their personal histories in relation to the personal time.
As a result, it is possible to speak about the ‘grandfather paradox’ and impossibility to change the future because of the reverse causation and necessary correlation between the personal and external time (Lewis 1976, p. 148).
Thus, relying on the causal sequence as the fundament for placing the events in relation to the time, it is important to predict the possibilities to change the reality of the past or future as well as impossibility to change anything because of the strong cause-and-effect relations.
If a time traveller performs his or her journey while visiting the past, the effects of this journey are observed in the present at the moment of the journey. Thus, these two processes are possible because all the events and phenomena are facts and not possibilities. In this case, the idea of fatalism is related to the four-dimensional world and reality.
On the one hand, the threatening effects are impossible because of the impossibility to change the reality and choose between the alternatives.
On the other hand, the threatening consequences are possible, and the time travel and the prevention of the negative effects are possible with references to focusing on the separated and even unequal time periods or amounts of the time in order to perform the journey (Nahin 2001, p. 102; Richmond 2001, p. 306).
To meet the serious threats caused by the time travel, it is necessary to concentrate on not changing the reality significantly in order to preserve the consistency of the casual loops.
The range of possibilities should be discussed as the range of facts because alternatives are not relevant in the Parmenidean perspective of the world where the past, the present, and the future are equally real and eternal and, as a result, are characterised by the real causes and consequences related to any acts.
One more satisfactory way to avoid any threats of the time travel is the ignorance of any effects and consequences because people really cannot change the past with the help of the time travel as they cannot change the past with the power of their thought (Goddu 2003, p. 17). Moreover, it is impossible to change the future that is why it is impossible to realise any actions in order to meet the possible threats appropriately.
Grey pays attention to the fact that “neither what has happened nor what is going to happen can be changed. It is a mistake to suppose that we can change either” (Grey 1994, p. 37).
From this perspective, any actions of a person in relation to this or that problem related to the time travel and its consequences seem to be useless because the future exist at the same moment when the problem is discussed, and it cannot be changed or influenced.
The time travel is the complex issue which involves a lot of problematic philosophical questions. The time travel is threatening because of the associated reverse causation in relation to the past and the future and impact on the casual loops regarding the personal and external time, which should be correlated. The present cannot exist if the past was changed, and this fact is the main threat of the time travel.
Nevertheless, the past, the present, and the future exist simultaneously, and it is impossible to change them. That is why, intolerable consequences of the time travel can be prevented not only because of avoiding changes in the past or future but also because of the inner impossibility of such changes in relation to the Parmenidean paradigm.
Reference List
Goddu, G 2003, ‘Time travel and changing the past (or how to kill yourself and live to tell the tale)’, Ratio, vol. 16. no. 1, pp. 16-32.
Grey, W 1994, ‘Some problems about time travel’, ATS1835 Study Guide, vol. 1. no. 1, pp 34-40.
Lewis, D 1976, ‘The paradoxes of time travel’, American Philosophical Quarterly, vol. 13. no. 2, pp. 145-152.
Nahin, P 2001, Time machines: time travel in physics, metaphysics, and science fiction, Springer, USA.
Richmond, A 2001, ‘Time-travel fictions and philosophy’, American Philosophical Quarterly, vol. 38. no. 4, pp. 305-318.