But doesn’t that really mean that everything happens all at once? That past time simply can’t be changed, and the future has already happened (although common sense says we can change it easily)? Maybe the character of the continuum of space-time is one in which not only the total amount of mass-energy is conserved. Maybe (to make sense of the
Terminator
paradoxes, at least), the continuum of “mass-energy-
time
” resists massive change as well. Some significant events in the continuum (like sending a T-101 into the past) might be able to affect causal sequences of events in a non-causal way.
This might sound like what hip scientists have talked about for a while as the “butterfly effect” (a mere insect wing flip may eventually produce the end of dinosaurs, while a wing flop would have had T-Rex’s descendants still thundering about today). But this reasoning nears absurdity. For example, let’s imagine that a Terminator intrudes on the famous Shakespearean sequence “For want of a nail, a shoe was lost; for want of a shoe, a horse was lost; for want of a horse, a kingdom was lost.” Some small adjustment in time that leads to something small like a missing nail may require only a minimal displacement in conserved mass-energy-time. But when the T-101 expects the missing nail to lead inevitably to the loss of the kingdom, enormous adjustments of the continuum would be required, and each major change would be increasingly resisted by the conservation of mass-energy-time. To tear the equivalent of Skynet out of the established future would require truly enormous adjustments, given the number of lives and other changes that Skynet’s existence shapes. Even the slightest change, even the “zig” rather than “zag” of a subatomic particle, would require enormous energy if it led to substantial and improbable subsequent changes. The upshot of all this is that if Einstein’s insights can be applied to time as well as to mass-energy, then when the T-101 claims, “Judgment Day is inevitable,” he is speaking as a confident scientist of time travel, not as a biblical prophet. In his story “Try and Change the Past,”
5
my father, Fritz Leiber, puts all this more compactly, elegantly, and personally, when he explains how very difficult any change in history must be:
Change one event in the past and you get a brand new future? Erase the conquests of Alexander by nudging a Neolithic pebble? Extirpate America by pulling up a shoot of Sumerian grain? Brother, that isn’t the way it works at all! The space-time continuum’s built of stubborn stuff and change is anything but a chain reaction. Change the past and you start a wave of changes moving futurewards, but it damps out mighty fast. Haven’t you ever heard of temporal reluctance, or of the Law of Conservation of Reality?
6
While the Credits Roll: Can We Stop, or Even Turn Back, Weapons Technology?
Like “Try and Change the Past,” installments of the
Terminator
saga show us that the future plays itself out deterministically, but not fatalistically. We learn in
Terminator 3
that the development of Skynet is only slightly delayed by the destruction of Cyberdyne. In today’s technology-rich culture, the law of the conservation of reality seems to lend itself to the truth of the idea that if a technology can be invented (especially a weapon-usable technology), it will be invented.
7
Technological developments seem inevitable: if not one Miles Dyson, then another.
We need to face the fact that genuine artificial intelligence is well on its way; and robotic physical force may, like in the
Terminator
saga, be coupled with it. La Mettrie’s and Turing’s insistence that there is no special spark to life suggests that evolution has more to say to us—perhaps it is now developing inorganic life. If the chimpanzee is nature’s way of making
Homo sapiens
, then why couldn’t
Homo sapiens
be nature’s way of creating the next phase in the evolution of life? Surely it is absurdly chauvinistic to think that we are nature’s final model. The real Terminators are coming, and we’d better start thinking about how to manage our marriage with them. Not today, but in time.
NOTES
1
Julien Offray de La Mettrie,
Man a Machine
(LaSalle, IL: Open Court Publishers, 1961).
2
You can find Turing’s essay in Douglas Hofstadter and Daniel Dennett, eds.,
The Mind’s I
(New York: Basic Books), 53-67.
3
For more on the Turing Test, and specifically about whether a Terminator cyborg could pass it, see the chapter by Greg Littmann in this volume, “The Terminator Wins: Is the Extinction of the Human Race the End, or Just the Beginning?”
4
For a dialogue on this issue and some suggested readings, see Justin Leiber,
Can Animals and Machines Be Persons?
(Indianapolis, IN: Hackett, 1985).
5
In Fritz Leiber,
The Change Wars
(Boston: Gregg Press, 1978), 81.
7
By the time that the Nazis had produced operational jet fighters in 1944, they were just months ahead of parallel British and American efforts. Radar, sonar, and digital computers had independent parallel development in several nations.
10
CHANGING THE FUTURE: FATE AND THE TERMINATOR
Kristie Lynn Miller
The future is not set, there is no fate but what we make for ourselves.
—Kyle Reese, in a message to Sarah Connor
You’re dead already. It happens.
—Sarah Connor to her psychiatrist
While
Terminator 2: Judgment Day
is in many ways an uplifting story of hope, it is in lots of ways philosophically perplexing. There are two contrary sentiments in the story encapsulated by the quotes above. Kyle Reese tells Sarah Connor that the future is not set and can be what we make of it. The message is clearly intended to suggest that Judgment Day, the day when Skynet launches nuclear weapons against the human population, killing three billion humans, is not inevitable. The other sentiment, expressed by Sarah to her psychiatrist while she is in custody, is that everyone around her is already dead, because Judgment Day will happen. She has knowledge of what
will
happen on August 29, 1997—Judgment Day—because she has been told what
has happened
in 1997 by Reese, who hails from 2029. For her, the future is fixed: the events of Judgment Day are inevitable.
From a philosopher’s perspective,
T2
raises all sorts of questions about the nature of the future and our ability to shape it. Which of these two sentiments is right? Can
both
be right?
Let’s start with Sarah Connor’s statement to her psychiatrist that he’s already dead because Judgment Day will happen. This is a sentiment she expresses frequently, and with this in mind, it’s clear that she sees her job as keeping John alive so that he can lead the human resistance after the inevitable event.
The Undiscovered Country: Does the Future Exist?
There are lots of reasons to think that Sarah is right that the future cannot be changed. Sarah originally learned about Judgment Day from Kyle Reese, a time traveler from 2029. From the perspective of Reese, Judgment Day is an objective fact—it has already happened in his past. Sarah probably has the view, shared by almost all philosophers who’ve considered the nature of time, that it’s not possible to change events that have happened in the past.
1
For instance, if Julius Caesar was assassinated in 44 BCE, then for us considering that fact today, it is not possible to change it. Yet many philosophers think that time travel is at least
logically
possible: they think that there is nothing logically inconsistent in the idea of time travel, even if they also think that time travel is not even close to being
technologically
possible.
2
So while it would not be contradictory to suppose that someone could travel back to ancient Rome, if Caesar was assassinated in the past, then there is nothing a time traveler could do in the past to alter that fact. Whatever the time traveler does in the past, he must already have done in the past, so he simply becomes part of the story of how Caesar was assassinated.
Let’s assume, then, that it’s not possible to change the past. If Judgment Day is a past event (at least relative to the time travelers from 2029), then that event can’t be changed, any more than the event of Caesar’s assassination on the Ides of March can be changed. To put it another way, if it is true in 2029 that Judgment Day
happened
in 1997, then it must be true in 1994 that Judgment Day
will happen
in 1997. Given this, it seems right for Sarah Connor to believe that events will unfold over the next three years precisely as she was told. So the future must be fixed, its circumstances unavoidable.
Many philosophers also think that the future is fixed because the future is as real as the present. And the events of
Terminator
and
T2
seem to make sense only if we share that assumption. After all, if a T-101 can travel back in time from 2029, then it seems as though 2029 has to exist for it to be
from
the time of the Terminator’s departure. Think about travel through space: if someone goes from A to B, it seems a safe assumption that both A and B exist, even if A does not exist exactly where B does. If A is
here
, then B is
there
, some spatial distance away.
3
According to one very common view in both physics and philosophy, the same is true for “locations” in time. Philosophers call this view
eternalism
: other times are real, just like other places. But just as spatial location A exists some
where
other than where spatial location B exists, so, too, temporal location T exists some
when
other than where temporal location T1 exists. The past and the future exist, say eternalists, but they do not exist
now.
Eternalists often say that in their view, the world is a big four-dimensional block composed of every point in time and space (or space-time) from the beginning of the universe all the way to its end.
4
If we suppose that eternalism is true, many of the events of
T2
make good sense. The Terminators can travel from 2029 because 2029 is a perfectly real location in space-time: it exists, but it is not located in 1994.
Eternalism is a very common view in philosophy, because it is supported by a lot of research in physics, in particular by Einstein’s theory of special relativity. Einstein tells us that depending on how fast you are moving, different sets of events will appear to be simultaneous. Suppose that the moment when the T-101 and the T-1000 arrive in 1994 (call it “T-moment”) is the present. T-moment and everything that occurs at that moment exist. Now introduce a new character into the story: the T-2000, a Terminator that is capable of moving so quickly that he approaches the speed of light. The T-2000 is simultaneous with Sarah at T-moment, so given that Sarah exists at T-moment, so does the T-2000. But this Terminator is moving
extremely
fast relative to Sarah. Special relativity tells us that the T-2000 will be simultaneous not just with Sarah, but with some events that Sarah understands as both in her future and in her past. Some of these events occur in 2029, during the resistance. But if the T-2000 exists, and for this Terminator the events of 2029 are objective facts, then Sarah should think that those events exist too, despite their being in her personal future. So she should think that 2029 exists. What special relativity tells me is that for
any
event in my past or future, anyone who might be moving relative to me will see that event as simultaneous with my continued existence. But because their speed allows them to coexist with other events, past and future, this means I should think that all of the events in my past and my future are as real as the events I experience as being in my present.
5
Not everyone accepts eternalism, though. Some think that something important distinguishes events in the future, the present, and the past. This idea hinges on the commonsense beliefs that the past is already written and unchangeable; that the present is alive and vibrant and especially real; and that the future is unwritten and full of possibility. Some philosophers think these differences in how we perceive time mark a real difference in the metaphysical nature of our universe. There are, roughly speaking, three different models that take seriously the idea that there is something metaphysically different about present, past, and future.
6
In one of these, only the present and the past exist, but as time moves on, what is
now present becomes past.
The space-time universe “grows” as new moments in time get added on to the end of the universe. This is known as the
growing-block model of the universe
.
7
Like eternalists, philosophers who accept the growing-block model think the universe is a four-dimensional block, but they believe it includes only locations in the past and the present. So the present moment is the moment at the “growing” end of the block. In the
Terminator
timeline, when 1994 is the present, Sarah and John Connor exist. So does Caesar (44 BCE) and the T-101 (1984), but the artificially intelligent machines of 2029 do not yet exist; or at least, this is what the growing-block model tells us.