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Free will is an illusion...


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Hello group :),


Here is a very interesting text about time travel:




Copyright © Michael Joyce 1996


10 Is time travel to the past logically possible? Is it logically possible


for you to travel back and have a conversation with your former self?


Could you kill your former self? Could you do anything to anyone, or could


they do anything to you, which you had not already done or had done to


you? Would you, or anyone else, in such circumstances, be a free agent?




Long a favourite topic of science fiction, the notion of time travel is


one that raises an enormous number of philosophical problems and


quandaries regarding causation, identity and the nature of time itself.


While it is fascinating to study these merely as hypotheticals, research


in the context of relativity has suggested some circumstances under which


time travel, to the past as well as the future, might be possible.


Views of time




The traditional view of time has been of something flowing inexorably


forwards, and in three distinct stages: past, present and future. The past


is fixed and unchangeable, the future is unwritten and does not exist yet,


and the present is what we are experiencing now. This picture is still the


most intuitive and natural way of viewing time. Since the theory of


relativity has become more widely accepted, time is no longer seen as


being so unique and separate, but as part of a four-dimensional framework.


It is still different to the three space dimensions in many important


aspects, but it can still be altered by factors such as speed and gravity.


It is relativity that gives a little credibility to the possibility of


time travel.1




Another view of time that I will mention is the "many-worlds" or parallel


universe view, in which a time traveller may not actually be visiting


their own past, but is actually travelling to a universe similar to his or


her original universe. Although it might be seen as an extreme extension


of some principles of quantum mechanics, the many-worlds hypothesis is a


useful way of sidestepping many of the logical and philosophical problems


of time travel. This is often thought of in terms of an extra dimension of


time, with different time-lines branching off because of the different


events in each system.2


Time travel is not a physical impossibility


A good simple description of time travel was given by David Lewis3 as


being when the personal time of the time traveller differs from the global


and historical time of the rest of the world. Lewis makes the analogy of a


personal time as a winding mountain railroad and external time as being


the distance as the crow flies to demonstrate that this does need a second


time dimension, but can fit in with our more usual picture of space-time


as a four-dimensional system. The railroad might take a meandering path,


even crossing over itself, but it is still contained within the same three


dimensions as a straight line between the railroad's origin and


destination. So too, a time traveller's personal time might different to


the global, external time of the rest of the world, but is still contained


within that global time.


Possible types of time travel




The type of time travel that is easiest to explain is travel into the


future, which could be accomplished by a spacecraft travelling at


relativistic speeds4. As the ship gets faster, time dilation slows time on


board the spacecraft relative to the planet it has left behind. For the


viewpoint of those remaining on earth, the astronaut has travelled into


the future. Travel in this manner is not usually thought of as time


travel, since the astronaut's personal time continues normally, but it


would have the same effect as a classic time machine (although it would be


disappointing for the astronaut to learn that there is no reverse gear on


the time machine). It also differs from the normal description of time


travel because, since the time traveller cannot return to his or her


natural time, his or her path does not cross over or duplicate itself.


The "Twins Paradox" described by travelling at relativistic speeds is not


one of time travel, but of time dilation and frames of reference. The


notion of time flowing at different paces is unexpected and difficult, but


not as counter-intuitive and confusing as the possibilty of travelling


backwards in time.




Like travelling into the future, travelling into the past would also


require several gross manipulations and incredible engineering feats in


order to exploit some of the more unusual effects of the theory of general


relativity. Many physicists are willing to ignore the possibility of time


travel to the past because it is so unlikely to occur and the energy


required to complete it render it extremely improbable5.


A number of schemes have been proposed to travel backwards in time. Some


involve a time that loops around itself6, others would use a rotating


black hole7, an accelerated wormhole8 or a cylindrical object so massive


that time would be bent right around and into the opposite direction9.


Although all of them differ to time travel as usually suggested in popular


fiction in that they also involve travel through space, the logical


complications are much the same.




Another type of time travel that might be much more possible, although a


little less dramatic, would involve tachyons. Tachyons are controversial


particles that travel faster than light, and, as a consequence of their


superluminal speed, backwards in time10. An ability to control these would


lead to the much the same philosophical problems of causation as a person


actually travelling backwards. While there would be no problems of


physically meeting oneself in a previous time, it might be possible to


communicate with oneself with tachyons, or even to use those tachyons to


cause (or at least attempt to cause) some events in the past.


Meeting a previous self


One scenario of backwards time travel that frequently raises concerns is


that of a time traveller travelling back and meeting themselves at an


earlier stage in life, often with the intention of giving themselves


advice in order to improve their lives or avoid a particularly traumatic


event. The first issue here is of the problem of duplication: is it


possible to have two "copies" of the same person at the same place and the


same time, and if so what is the difference, if any between the two


people? The second is the problem of the inconsistencies between the


traveller's memory of the past and the events that transpire once he or


she goes back to the past.


In David Lewis' description of time travel, the time traveller's world


line might have discontinuities in relation to the rest of the "normal"


timeline11, so he has to go to great pains to explain the continuing


identity of a time traveller as not only having the same physical


characteristics as the time traveller's previous existencein their


personal time, but also an element of causal connection. The methods of


time travel mentioned above involving travel through space as well do not


have these discontinuites, so personal identity is easier to ascertain.




If a time traveller did travel back to a time that he or she had already


lived through, would we be able to say that the two people are one and the


same? There would obviously be some physical differences in age and


appearance and mental differences in the older time traveller's extra


memories and experiences, but these differences would not normally lead us


to make a distinction between a young and old version of an everyday


non-time-travelling person as being different people. Although time travel


seems more complicated, there is no reason why a time traveller's personal


time line could not cross over itself like a mountain railroad crosses


over itself on a bridge.


Inconsistency with the past


The second problem of meeting oneself as one travels back in time is


really just a simpler version of the grandfather paradox detailed below.


If the time traveller does meet with him or herself in the past, then it


follows that the meeting will be a part of his or her own memories and


past. Unless the two-dimensional time framework is introduced, the time


traveller must have a memory of being visited by an older version of


himself in his or her youth. The possibility of a time traveller acting in


a way that was inconsistent with the known past raises a few interesting




The Grandfather Paradox


As the most extreme example of changing the past, a hypothetical is often


envisaged whereby the time traveller visits the past with the intention of


killing his or her own grandfather or grandmother so that the time


traveller will never be born. This is usually known as the Grandfather


Paradox12. Numerous variations on the theme exist, but the basic question


remains the same: if time travel to the past were possible, would it be


possible to change the past, and moreover to change it in such a way as to


make the time traveller's existence impossible?


The simplest way to avoid this paradox is by invoking the many-universes


theory of time. In this case, the time traveller actually kills the person


corresponding to his ancestor in a different time, leaving his own


ancestor (and thus himself) untouched13.


To many, the two-dimensional-time solution is a cop-out, since the time


traveller is not visiting his or her own past, just a past that is


remarkably similar to it. Even though the time traveller can perform


actions that are inconsistent with the past as he or she know it, these


actions will still have to be consistent with the timeline of that


particular universe.


Lewis reminds us not to confuse "logically impossible" with physically


incapable14. If we look at the time traveller as just another occupant of


that time armed with a gun and all the skill required to kill his target,


we would not say that it is impossible for him to complete the task.


However, this ignores the important fact of the time traveller's past. We


know that the time traveller's grandfather did not die at that stage, so


the assassin could not have succeed. We can say the same thing of any past


event: John Hinckley could have killed Ronald Reagan when he shot him in


1981, but didn't.


Doing anything else inconsistent with history


The case of killing your own grandmother or grandfather is a particularly


interesting one because it involves not only a contradiction with the past


as the time traveller knows it happens, but also a paradox that shows why


such an inconsistency is illogical. Although the existence of the time


traveller's grandfather is of obvious importance to the time traveller, it


is not significantly different from any other act that is inconsistent


with the time traveller's past, whether he or she knows about it or not.


The time traveller's past exists not just for the time traveller, but also


for everyone else alive in his or her "natural" time. If the time


traveller killed someone else or gave them the blueprints for an


invention, the records of the time traveller's natural time would have to


show events that correspond with the actions of the time traveller in the


past, regardless of whether the time traveller knew if that was how things


would pan out or not.


Free will


The worrying aspect of looking at time travel in this way is that it


eliminates free will for the time traveler. Although the time traveller


believes that he or she is able to kill a particular person, they are


destined to fail since the events of that time have already been fixed,


regardless of whether the time traveller knows of them or not.


We think of the future as being variable and determined by the actions we


take in the present. The presence of a time traveller in our time would


shatter this illusion. Our future is the time traveller's past. If he


cannot change it, then neither can we. Whatever is written in the history


books of the time traveller is what we in the present will do.


If the future is fixed as well as the present, we might look at time as


like a movie film strip. To everyday people, the film moves past the


projector at a steady rate and we see only the present. We know what has


already happened in the movie, but can only guess at what will happen


next. To a time traveller, the movie is unravelled and spread out on the


floor. The whole of the movie is fixed, regardless of which frame the time


traveller believes he or she is in. At no stage can anyone alter the


course of events once the film has been processed and fixed in its nature.


In a two-dimensional description of time, there is no paradox in a time


traveller killing what appears to be their own ancestor, so it at first


looks as though free will still exists. Although the time traveller might


seem to be able to do whatever they want, whatever they do will still have


to be consistent with the events that transpire within the timeline that


the time traveller now occupies.


Imagine two unrelated time travellers both travelling to the same


timeline: one is travelling to his or her own past (Traveller-A) and the


other to a time-line that is merely similar to his or her own past


(Traveller-B). Traveller-A will be in exactly the same situation as if he


or she were in a one-dimensional time situation, and will be unable to do


anything inconsistent with his or her own past. Similarly, Traveller-B


will also be unable to do anything that would be inconsistent with


Traveller-A's past. Since the events forward of the time when Traveller-A


and Traveller-B meet are fixed for that timeline, the situation is no


different to a one-dimensional time situation.


Changing the past in fiction


Depictions of time travel in science fiction commonly allow the


protagonists to intervene with and interfere with the past, although the


travellers usually take enormous pains to avoid doing so. Two-dimensional


depictions of time apart, the most logical of these depictions is in


stories where the memories and records of the past that the time


travellers have change to reflect the past: usually instantaneously, but


sometimes as a flow-on effect of the change. Such a notion is plausible,


so long as the changes they make do not logically rule out the fact that


the travellers were able to make these changes. In such a situation, free


will is preserved in all aspects but those that will make it impossible


for the travellers to exist at that point in time. Of course, the problem


with this is in determining what changes would rule out this existence:


killing your own grandfather is obvious, but what of merely preventing two


of your distant ancestors from meeting, or preventing the time machine


from being invented?


The more usual story depicted in science fiction is one where the


traveller's past does change, but he or she retains her memory of the past


as it was. This story is inconsistent from a logical and philosophical


point of view, but makes for a more interesting and conventionally


comprehensible narrative.




For a time traveller, the distinctions between past, present and future


disappear, so that the future may be fixed and unchangeable. If this is


the case, free will is gone too, not only for the time traveller, but also


for all the other inhabitants of his or her past. This conclusion is so


extreme that we may be better to reject the notion of time travel and keep


our precious free will than to accept this consequence of the general


theory of relativity.




Davies, Paul (1995) About Time Penguin Books


Horwich, P. (1987) Asymmetries in Time: Problems in the Philosophy of


Science, MIT Press, US


Lewis, D.K. (1976): 'The Paradoxes of Time Travel', American Philosophical


Quarterly 13


pp 145-152. Reprinted in Source Materials 136-220, 1996




Davies, Paul (1995) About Time Penguin Books, p 33


Lewis, D.K. (1976): 'The Paradoxes of Time Travel', American


Philosophical Quarterly 13


pp 145-152. Reprinted in Source Materials 136-220, 1996 p 231


Ibid p 137


Davies p 234


Ibid p 244


Ibid p 246


Ibid p 244


Ibid p 246


Ibid p 245


Ibid p 234


Lewis p 136


Lewis p 141-146


Ibid p 146


Ibid p 143


Copyright © Michael Joyce 1996.Created by Michael Joyce


[email protected]


Last Modified October 25, 1996


<This message has been edited by Marcelo (edited 24 June 2000).>





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  • 14 years later...
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Fascinating that this was posted 15 years ago (???) and no one commented... In fact, the title is catchy and the contents are interesting, but I beg to disagree with it. I don't think that free will is an illusion, but at the same time I do agree that most people don't have free will and just march mechanically in the existence.


"For a time traveller, the distinctions between past, present and future


disappear, so that the future may be fixed and unchangeable. If this is


the case, free will is gone too, not only for the time traveller, but also


for all the other inhabitants of his or her past. "


When past, present and future disappear it's when we achieve a superior knowledge so that's when we in fact have free will.



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Imagine then that your consciousness (or soul if you will) is creating a worldline depending on the decisions it makes. All outcomes are possible and inevitable in the great spectrum of everything. So I say the the universe you experience is yours and yours alone. And while we may not realise it, everything around us is fluid and malleable, changing specificly because of our input. Whether or not we do this consciously is up to us.


"Pay attention to these petals, Steven. The petal’s dance seems improvised, but it is being calculated in real time based on the physical properties of this planet. With hard work, and dedication, you can master the magical properties of your gem and perform your own dance!”





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I have always lived by the firm belief that both are true. We have a predestination... however, how we get there is based on free will. Kind of like the Time Machine. No matter how many times he went back in time to stop her death, all he did was change how she died. We all have certain things in our lives that are preordained. How it happens and how we get to the point for it to happen is up to us, but it happens exactly when it is suppose to happen. Just like death. You are given a date in which you are going to die. When that moment arrives, nothing you do will prevent it or stall it. However, how you died is determined by you.



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