Persons May Travel Faster Than the Speed of Light and Are Not Wholly Physical

Mark Walker (

1.                 Introductory

According to general relativity and our best inventory of the fundamental physical magnitudes of the universe (strong and weak nuclear binding force, gravity and electromagnetism), the time interval between an object being at point A and then B is equal to or more than the time interval that would be required for light to travel from A to B. The following story suggests that persons are not bound by this law. Of course, any two-bit sci-fi story can describe faster than light travel. The difference is that this story is consistent with our best physical theory. The upshot is not that our best physical theory is wrong, but that persons are not entirely physical. In other words, the explanation for why faster than light travel is possible, yet consistent with our best physics, is that persons are not wholly physical. I will present the story, and then discuss possible philosophical implications.


2.                 The Story:

Evelyn was on Earth; her identical twin sister Sara was on a space station orbiting Saturn. Sara yearned to be home with her beloved cat, Puffy, on earth. Evelyn longed to look out of a telescope far away from Earth’s light pollution. Evelyn and Sara plotted a solution. The following week they used a “Brain State Transfer Devices” to swap places. Here is how the plan unfolded (all times are given in Greenwich standard time):

2am: Evelyn and Sara were anesthetized. Evelyn’s brain was scanned down to the subatomic level.  Sara’s brain too was scanned down to the subatomic level. The process for a complete scan took 30 minutes.

2:30 am: The information about the nature and location of each particle of Evelyn’s brain was sent at the speed of light to Saturn. The information about the nature and location of each particle of Sara’s brain was sent at the speed of light to Earth.

3:30 am: Radio signal containing the information about Evelyn’s brain arrived at the space station and information about Sara’s brain reached Earth.

4:00 am: The integrity of the information received was confirmed at both points. Earth signaled Saturn and Saturn signaled Earth that the information from the respective brain scans were received in good order.

5:00 am: Scientists on Saturn and Earth received the news that the information previously sent arrived in good order.

6:25 am: Doctors checked the vitals of Evelyn and Sara one last time and confirmed that each patient was still anesthetized and doing well. 

6:30 am: Brain State Transfer devices whirled into action at both locations. Within half an hour, molecules in each brain were rearranged according to the information previously sent. It turned out that Evelyn’s brain was slightly larger, but this possibility was anticipated. Both patients had had extra-large meals before being anesthetized. The additional mass to remake the brain in Sara’s body to be exactly like that of Evelyn’s was obtained from molecules extracted from Sara’s digestive system. The extra mass in Evelyn’s brain was removed to Sara’s digestive track to make an exact duplicate.

7:00 am: The operation was complete. The patient on Earth awoke and claimed to be Sara; on Saturn the patient claimed to be Evelyn. When Sara returned to work, her coworkers were pleased and surprised to see her. Sara’s friends invite her out for a drink and to reminisce about old times. Her husband and family too are happy to see Sara home. Even Puffy is pleased to see her—as much as cats are ever pleased.


3.                 Faster than Light Travel

The reason for thinking that faster than light travel is possible is that, according to the story, Sara went from Saturn to Earth in 35 minutes (or less), whereas light takes an hour to traverse this distance. We may summarize the faster than light argument thus:


P1: If faster than light travel is impossible, then either the physicians or the patients are mistaken.

P2: Neither the physicians nor the patients are mistaken.

C: Faster than light travel is possible.


The reasons for thinking that P1 is true are the ones just noted:  the physicians on Earth testified that Evelyn was on Earth and fine at 6:25 am and the physicians near Saturn testified Sara was in good shape at the same time. At 7:00 am the patients awoke and claimed to be in a different location. Since the time interval is only 35 minutes, either the physicians or the patients must be wrong, for 35 minutes is less than the hour that would be required for light to travel from point to point.

As for P2, there seems little reason to doubt the physicians’ report at 6:25 am. The patients were anesthetized as in many operations. If something had gone wrong, and the patients were revived at 6:25 am, there is no reason to doubt that Sara would have woken up at the space station and Evelyn on Earth.

More interesting is the idea that the patients are correct in describing themselves as having transferred locations. This is perhaps the crux of the matter. We will examine it below.


4.                 Not Wholly Physical

The reason for thinking that persons are not wholly physical is simply that it is impossible for something wholly physical to be in two different locations faster than light could traverse the same distance. We may summarize the not wholly physical argument thus:


P3: If the persons are wholly physical, then either the physicians or the patients are mistaken.

P2: Neither the physicians nor the patients are mistaken.

C: Persons are not entirely physical.


The basic intuition undergirding P3 is the following:


Wholly Physical Identity Condition (WPIC): If X and Y are identical and X and Y are wholly physical, then X and Y must share a preponderance of matter or share a preponderance of matter with intermediate stages where each intermediate stage shares a preponderance of matter with the preceding and subsequent stages linking X and Y.[1]


Think of the ship of Thebes. If decaying lumber comprising the ship is gradually replace a plank at a time, it is possible that the ship of Thebes may last hundreds of years. The ship several centuries hence may no longer be comprised of any of the original lumber. Yet a necessary condition for the survival of the ship of Thebes is that it maintains a preponderance of its physical matter from one stage to the next. So, suppose 1% of the ship is replaced every year, and so in a hundred years no original lumber remains. This does not violate WPIC because a preponderance of matter is maintained from one year to the next. If Sara wakes up on Earth after the brain state transfer, then she is not wholly physical. For the assertion that she continues to exist on Earth violates WPIC—no preponderance of matter is shared between Sara on Saturn and Sara on Earth, nor are there intermediary stages that share a preponderance of matter.

I make no positive claims about the non-physical “essence” of persons other than that they cannot be described in purely physical terms. At one extreme is the traditional dualist assumption that persons have an immaterial soul that is not subject to the laws of physics. This soul travels faster than the speed of light. At the other extreme is the idea that at least part of the essence of persons is an abstract “pattern”. This pattern describes the psychological continuity required by the weak psychological continuity theory. Physicalists need then provide an account of the ontological status of abstract entities. The story is consistent with these and other non-physicalist theories, but it does not necessitate one over the other.


5.                 Not Somaticism

The obvious means to deny these arguments is to say that Sara, Evelyn, and their friends, families, and colleagues are mistaken in believing that they have switched locations. A theory of personal identity that fits nicely with this reaction is somaticism: the view that bodily continuity is necessary for the preservation of personal identity. Since the particles that comprise Sara and Evelyn’s bodies prior to the operation have not been transported across the solar system, the somaticist will deny the claims by the patients who have awoken from the surgery. Somaticists will say that Evelyn remains on Earth; and Sara on Saturn.[2]

I will rehearse four reasons for thinking that somaticism is wrong:

5.1  What We Care About in Others is Not Physical Continuity

Imagine that as far as Evelyn and Sara’s friends and family know, the two swapped places in the old-fashioned way: they took the one month journey between the two planets in a fusion rocket. (They each stayed in hiding on their respective planets to make everyone think they were traveling.) ). None of their friends or family can tell that the person on Earth is not Sara and that the person on near Saturn is not Evelyn. The reason, of course, is that they appear to think and act just as people have come to expect. The person on Earth pampers Puffy just as Sara would. The person on Earth appears to have the same quirky sense of humor that Sara has. When they reminisce with her, the person on Earth remembers everything that they would expect Sara to remember. The same of course for the person near Saturn: the person there has the same love of astronomy as family and friends have come to expect Evelyn to have. Suppose a year later, the news about the brain state transfer is announced. We would expect friends and family to be mildly surprised, but not to start treating the person on Earth as Evelyn rather than Sara. We can imagine Sara’s husband saying that he married Sara for her keen mind and sparkling personality, not because she happened to be some particular collection of atoms. He says he is not particularly upset by the fact that the keen mind and sparkling personality is located now in the body formerly inhabited by Evelyn.

5.2 What We Care About in Ourselves is Not Physical Continuity

Here is a version of the argument:

The Vorlons, with their ability to see into the future, say the news is grim. In less than twelve hours you will have a massive stroke that will cause you to lose many of your memories and some mobility, and impair your intelligence. Your stroke will not be as bad as some: the damage from the stroke will not leave you completely cognitively impaired, but you will no longer be able to work as an academic. You will have to find some relatively mindless job befitting your new level of intelligence, perhaps in academic administration. Friends and family will say that your once keen memory has been dulled such that your memory is now fuzzy, and you seem to remember the most superficial things. It is a shame, and totally unexpected at your young age. Even with their immense power, there is nothing the Vorlons can do to prevent the stroke. They provide a radical alternative: creating a perfect replica of you – down to the molecular level – with the exception that the problems with the arteries to your brain will be fixed in the body replica. They insist, however, that only one body can survive. You must choose tonight whether the replica or your current body survives.

Most people I’ve asked about this would rather see the replica survive, for the replica best embodies what is most important about you: your memories, your personality, your beliefs and desires. None of this is to say that the loss of one’s body is trivial. One can be quite attached to one’s body; but, when given this tragic choice, more of what is essential to you as a person survives in the replica.



Perhaps it might be remonstrated thus: “If I survived in a brain damaged state, I would be a terrible burden on my family and the world. It would be better for my family and the world that I died and a replica replaced me.” To avoid this objection we can simply stipulate that the decision is to be entirely selfishly motivated, and that we know this about your preferences: you would rather survive a stroke than not survival at all. So, if the Vorlons did not offer you a chance to survive as a replica, you would rather live after the stroke than die. If the choice is still to have your present body die (the one with the bad arteries), then this can only be explained by thinking that you will survive as a replica.


It may be thought that even the most selfish person might prefer death if it meant something else he or she valued might result, e.g., you value the finishing of your novel more than you value your own life. If a replica of you can better realize this project, then it is consistent with selfishness to prefer death to oneself for the sake of the great unfinished novel. Again, we may simply stipulate around this objection. We may say simply that what you want most is for you to finish writing the novel, not someone else. If you die, you would rather it remain the “great unfinished novel” than be finished by someone else. If this is your most important desire, then preferring the stroke body’s death cannot be explained away by the thought that what you wish for is the completion of your projects.


It is worth noting that not all somaticists are likely to be convinced by this example. But it should convince a few, and points out one of the heavy costs of somaticism.[3]


5.3 Perpetual Molecular Replacement

Here is a version of the argument:


Suppose that every night when people sleep their bodies (including their brains) are scanned by a swarm of nanobots and a molecule for molecule identical body is beamed from a hidden alien spaceship in orbit; the old body is vaporized in a manner that is undetectable by the human eye. Scientists discovered this fortuitously: physicists noticed a spike in neutrino levels every time psychologists in the adjoining lab conducted sleep experiments. Intrigued, scientists built a chamber to isolate subjects from neutrino influences and then had test subjects sleep in the chamber. Once the experiment was initiated, a hologram of a Vorlon appeared in the lab and spoke thusly:


We are an ancient race known as the “Vorlons.” We battled another species, the “Shadows,” just as your species was beginning to evolve on this planet. One of the toxic effects of our war was a type of radiation that kills all higher intelligences within three days. We have no way of eliminating the radiation, but we have left advanced technology to recreate your bodies from different molecules every day so that the radiation will not harm you. We left the galaxy eons ago. You are hearing this message now because you have advanced technologically to the point where you can detect our technology. If you interfere with our replicator technology, you will quickly die of radiation poisoning.


What should we make of this? It is clear that dismantling it is out of the question since all humans will die within three days. If you are a somaticist, you must conclude that you have been alive only for a very short while. In fact, you have existed only since last night. After all, the physical continuity of one’s body has lasted only this length of time. However, most of us, I think, would conclude the opposite. That is, that we have existed for years: that we do not cease to exist every night and a new person comes into being.


This example may not be a decisive refutation of somaticism, but it does at least pull out one pillar of support. Somaticists ask why so many would be reluctant to step into the Teletransporter that Parfit describes, intimating that our reluctance has to do with the fact that our bodies will not survive. The retort, suggested by this example, is that the reluctance is explained more simply as a fear of the unknown. Contrariwise, the somaticist must now explain how so many people could be mistaken about their own identity retrospective case; after all, it seems very likely that, upon learning about the Vorlons’ technology, most would conduct their lives as if they hadn’t just come into existence that day. Who is going to say such things as: “I do not have to look after these children you call mine: how can I have children if I myself was born today. I can’t use this driver’s license, it is someone else’s  I was just born today. I’m not qualified to teach any classes: a postgraduate degree is required, which takes years to earn, and I was just born today?”[4]


5.4 Identity and the Law

The fourth reason to reject somaticism is that it is simply not a doctrine we could live with. Suppose somaticism was the law of the land. Let us imagine earlier in the evening, before her operation, Sara killed her unfaithful lover and transferred all her assets to her sister Evelyn’s account on Earth. The operation takes place as described. The police on the space station are there when the patient on Saturn awakens. They charge her with murder. The patient protests that she has no memory of killing anyone. As far as she is concerned, her last memories are of being on Earth. She explains that she has the memories of Evelyn, not Sara. Sara tricked her into performing the brain state transfer so that she would do the time for Sara’s crime. Somaticism sins against our sense of justice: if the court incarcerates the person on the space station for the crime, the real perpetrator has escaped justice. The person who should be put in jail is the person on Earth. The reason for this is that the person on Earth is Sara.[5]

6.     Weak Psychological Continuity Theory of Personal Identity:

A more plausible account of personal identity takes psychological continuity to be the grounds of identity of persons through time:


Weak Psychological Continuity Theory of Personal Identity:  X and Y denote the same individual if there are overlapping sequences of psychological properties including intentions, actions, memories, beliefs, desires and abilities. 


Assuming the weak Psychological Theory of Personal Identity, each patient is correct: we have good reason to suppose that what each patient says upon waking is true and that their friends and families are correct in their attribution of identity claims. The patient on Earth has the beliefs, desires, and memories that overlap with the beliefs, desires and memories of the individual anesthetized on Saturn and vice-versa.  For example, the patient who awakens on Saturn claims to have a burning desire to look through a telescope without light pollution. The patient who awakens on Earth says she misses her cat Puffy. This is just what people have come to expect of Sara and Evelyn. The theory also provides the result in the case of the big stroke: it would be entirely rational for you to ask for the replica to survive and not your present body. With psychological continuity theory, you survive in the replica body. It also gives the correct result in the perpetual molecular reconstruction case: if this scenario were true, we would not all be less than one day old. We would simply live in new bodies each day. Finally, psychological continuity theory would instruct the police to arrest the patient on Earth for the crime committed on the space station.

The term ‘weak’ is used because the theory suggests only a sufficient condition for personal identity through time. So, just because there is no psychological continuity between X and Y, this is not enough to show that X and Y is not the same person. For example, Terri Schiavo was reportedly “brain dead”, meaning that there was no detectable higher mental life. If psychological continuity is a necessary condition for survival, and the body referred to as ‘Terry Schiavo’ lacks any psychological states, it would follow that the entity in the bed referred to as ‘Terry Schiavo’ is not Terry Schiavo. However, the view put forward here takes no position on whether bodily continuity itself might be sufficient where psychological continuity is lacking.

Some versions of psychological continuity highlight certain psychological states as particularly important, e.g., Locke thought continuity of memory is of particular importance. For our purposes, we need not highlight any particular psychological states. If Evelyn’s brain is rearranged to have exactly the same atomic structure as Sara’s brain at the time of the scan, we will suppose that all relevant psychological states will be preserved. Sara’s beliefs, desires, memories hopes, dreams about her cat and other matters will survive when she awakens in Evelyn’s body.

7.     Consistency with Physicalism

The story is consistent with our best physical theory, but it is inconsistent with physicalism. Any apparent tension between these two claims can be alleviated by stipulating that the aim of physical theory is a complete and true account of everything that is physical. Physicalism is the view that everything that exists is physical. It is the latter claim that the story challenges.

Still, it may sound strange to think that this story is alleged to challenge physicalism.  After all, it does not appear to appeal to the dualist’s traditional two substances: physical stuff and soul stuff. Of course, as noted, one could explain how it is that Sara was near Saturn and then on Earth in less time than it would take light to travel this distance by appealing to soul stuff. If we have souls like angels, and these can travel faster than the speed of light, then this would be one explanation. However, nothing like this is offered in the story. The idea that memories, beliefs, desires and other personality traits would be recreated by rearranging the molecular structure of Evelyn’s and Sara’s brains sounds like something a physicalist would say.

It is certainly true that the story assumes that identical molecular structure will result in the same psychological states, and that no appeal to an ethereal soul is made, but this is not sufficient for physicalism. The reason, again, is that these assumptions are consistent with faster than light travel; and faster than light travel is inconsistent with our best physical theory. We can turn the point around: if one insists that persons are entirely physical, and admits that Sara and Evelyn may switch places as described in the story, then one will have to reject our best physical theory in order to preserve physicalism. One can’t have it both ways: either our best physical theory or physicalism must go.





[1] The term ‘preponderance’ is intentionally vague. For the purposes of this argument we don’t even need the assumption that physical continuity requires more than 50% mass in common between successive stages, it could be lower than 1% and the story would still work, since there is no discernible exchange of physical stuff between the patients.

[2] Alternatively, somaticists might say simply that Evelyn and Sara died rather than switched places. New persons have been created by the brain transfer device. This would be to interpret bodily continuity as merely necessary for continuity of identity. Nothing is gained by running through this alternative, so we will ignore it for present purposes.

[3] M. Walker, “Personal Identity and Uploading,” Journal of Evolution and Technology 22, no. 1 (2011): 37–52.

[4] Ibid.

[5] Ibid.