C.S. Lewis has ruined Doctor Who for me. Well, not really, obviously. But Lewis made one simple statement about time travel once that has spoiled ever other time-travel story I've encountered ever since. So I'm going to share that with you, then talk about a couple of time-travel stories and their problems.
The Dark Tower and the Problem of Bodies
Even if you are a super C.S. Lewis fan, you may not have read The Dark Tower. It is a fragment, just the first few chapters of a projected novel. [There is an interesting controversy about this novel]. I do recommend reading it; I love it and am distressed that CSL didn't finish it. If he had, it would have been a powerful part of his extended Ransom cycle, along with Out of the Silent Planet, Perelandra, That Hideous Strength, and The Screwtape Letters. In fact, if Tolkien had finished The Fall of Arthur, all of CSL's Ransom books and everything Tolkien every wrote and all of Charles Williams' Arthurian poetry could have been mapped on to one another in a massive multi-layered totalizing mythology. But that's a totally different topic!
Anyway, The Dark Tower is a creepy story about a scientist who has invented a "chronoscope" with which he can watch some other time period. He doesn't know what time period it he is watching, whether past or future, and as the story progresses, the characters watching this time unfold start to suspect it's more like a parallel time, or the same time in a parallel universe, or perhaps even a glimpse into Hell. The action heats up when two characters are apparently exchanged between Othertime and our time, with a wild chase ensuing. It breaks off in the middle of a sentence, just as things are getting exciting. The best bit, from a literary-philosophical-science [fiction] point of view is this discussion (which I was delighted to find already transcribed here):
“Of course,” said Orfieu, “the sort of timetravelling you read about in books -- time-travelling in the body -- is absolutely impossible.” ...And that has ruined it for me. Right there. With his usual clean cuts, CSL has sliced open the heart of time-travel fiction and revealed its emptiness. Really, I can't see any way out of that difficulty. Can you?
“Absolutely impossible?” said Ransom. “Why?”
“I bet you see,” said Orfieu, glancing towards MacPhee.
“Go on, go on,” said the Scot with the air of one refusing to interrupt children at their play. We all echoed him.
“Well,: said Orfieu, “time-travelling clearly means going into the future or the past. Now where will the particles that compose your body be five hundred years hence? They'll be all over the place -- some in the earth, some in plants and animals, and some in the bodies of your descendents, if you have any. Thus, to go to the year 3000 AD means going to a time at which your body doesn't exist; and that means according to one hypothesis, becoming nothing, and, according to the other, becoming a disembodied spirit.”
“But half a moment,” said I, rather foolishly, “you don't need to find a body waiting for you in the year 3000. You would take your present body with you.”
“But don't you see that's just what you can't do?” said Orfieu. “All the matter which makes up your body now will be being used for different purposes in 3000.”
I still gaped.
“Look here,” he said. “You will grant me that the same piece of matter can't be in two different places at the same time. Very well. Now, suppose that the particles which at present make up the tip of your nose by the year 3000 form part of a chair. If you could travel to the year 3000 and, as you suggest, take your present body with you, that would mean that at some moment in 3000 the very same particles would have to be both in your nose and in the chair -- which is absurd.”
There are, of course, many other problems with time travel.
The Blue Yonder and The Problem of Infinite Recurrence
One problem is the simple fact that if you went back in time and changed something, well then, it was changed in the past, so it would always have been that way. There would be nothing for you to change.
Nearly any time-travel movie or show would work as an example. I'm going to use The Blue Yonder, one I remember vividly from childhood. In this film, a little boy grows up knowing that his grandfather had died while attempting to make it across the Atlantic in a solo flight. Then the boy finds a time machine, goes back in time, and changes the past so his grandfather makes it.
Here's the difficulty. If the boy had done that, then since it was in the past, his grandfather would always already have made it, and the boy wouldn't know any differently—so then he wouldn't go back into the past to make that change, which means it wouldn't have been made, and he would have to go back, and we've got ourselves stuck in a strange loop.
Another big problem has to do with the way in which time-travel stories are told.
Harry Potter and The Trouble with Narrative
Harry Potter and the Prisoner of Azkaban is the perfect example of this problem. Here's how it goes.
It is important to understand that there are two passes in the narrative: two trips, as it were, through the same period of time, the same three hours one evening. (Watch this great split-screen presentation):
Narrative #1. Harry, Ron, and Hermione go to Hagrid's hut to console him over the upcoming execution of Buckbeak the hippogriff. Events unfold all the way until the moment Harry and Sirius are about to have their souls sucked out by dementors, when Harry sees a young man across the lake. This person sends out a stag patronus, which scatters the dementors and saves Harry.
Narrative #2. This is the second pass. Keep in mind that this is the same three hours as described in #1 above. It is another narrative—another story told to the reader/viewer, but it is the same set of minutes that the characters are passing through in linear fashion, 4:00, 4:01, 4:02, etc. Harry and Hermione go back in time, conveniently acquiring a second set of bodies in complete defiance of C.S. Lewis' principle described above. But they travel a different path physically, though it is the same path in time. Events unfold again, the same events, just seen from a different perspective, until Harry and Sirius are about to have their souls sucked out by dementors. This time, Harry is on the other side of the lake, waiting for the young man he thinks was his father. At the last minute (at the same minute as in the sequence before), he realizes he saw himself, so he sends out the stag patronus.
Now, here's the problem with the unfolding of the same narrative twice, or two narratives in one time period. In order for that to work—for Harry to mistake himself for his father—he had to have traveled through story #1 FIRST, then through story #2 (the same way in which the reader/viewer encountered those stories)—but it's time travel, so the two stories happened at the same time. There was no first story and second story—that's only a convention of story-telling, not a chronological reality. Harry could just as well have gone through the second story first, but really he went through both at the same time, so he would have known the figure with the stag patronus was himself, not his father, because, well, because it was himself and he was doing those actions at the same time.
I was of Two Minds
There is, of course, another enormous problem there with both the narrative and the bodies: what about the mind? If you somehow magically got an extra body to run around in the past with, watching your other self, what about your consciousness?
In Harry Potter, the reader is led to assume that time-travel creates two consciousnesses, one for each body (the “past” body that is going through its timeline naturally, and the “present” body that is going through its past timeline by unnatural means). But then these two consciousnesses are unaware of one another. Even supposing, for the sake of the fantasy, that time travel did create two bodies (and thus two consciousnesses), why does that then mean that the two consciousnesses would be unaware of one another? Why would they not be in communication? And why would their memories be different? The “past” body contains a consciousness with a memory up to its current moment on its natural timeline, while the “present” body that has traveled back contains a memory up to the moment that it left its natural timeline. Why wouldn't traveling back in time erase the memories back to that previous point? Or why wouldn't traveling into the future dump “future memories” into the consciousness of the traveling body? Or why wouldn't traveling either direction give unlived memories to the non-traveling body?
Well, again, simply because of narrative. Simply so that the story works, so that the story can be told.
“Blink” and the Causeless Circle
Now, “Blink” is one of the better time-travel stories I've come across, and one of the best episodes in all of Doctor Who from that point of view. But there are some problems.
First, the Angels chucked Billy back in 1969 so that they could consume the life-energy he would have had if he had kept living out his years naturally. So, there's just random extra life-energy waiting for him in 1969? That doesn't make sense.
And there's another problem that's actually a beautiful one: it's really quite a lovely philosophical conundrum rather than a flaw in the story. Let's see if I can express it—this is a tough one. Here goes.
Sally reads warnings that the Doctor left for her on the wall. He traveled back in time from the future to leave those warnings. He knew she would be there at that time and place because he had the advantage of the future, so he could “look back” and warn her. OK, so far so good. Same thing with the letter from her friend Kathy.
- Billy got kicked back into 1969.
- He sat down with the Doctor and recorded the Doctor reading that transcript.
- Sally watched the dvd and had a conversation with the Doctor.
- Larry transcribed the conversation.
- Sally met the Doctor and gave him the transcript in 2007.
- The Doctor got chucked back to 1969 where he met Billy and recorded the conversation.
Did I get that right?
OK, so you see how neatly that loop avoids the problem created in The Blue Yonder. It's not a strange loop, because Sally didn't change anything. Nobody changed anything. Instead, they acted out a series of events that would have gone otherwise if they hadn't had information that relied on time travel for its transmission. Very good, Moffat!
The problem of bodies is averted: each person's one body is taken from a time period and put into another. There aren't two bodies. (Of course there are in other episodes, in which the Doctor meets himself, or Rose or Amy meets her younger self). Sally stays in her time period, and Kathy's and Billy's bodies move from one era to another without leaving a body behind. (Of course, that doesn't answer the question of where they got the molecules to make up a body in that period, though). Decent job, Moffat.
They don't have two minds, then, either: as a matter of fact, the way the story works depends upon the limited knowledge of a single, time-bound consciousness for Sally, and a single, time-moveable consciousness for the Doctor. Nice work, Moffat.
So then, what's the problem? Well, it's that the events in “Blink” constitute a nice chain of cause-and-effect, but that the final effect is the cause of the first cause.
Aristotle would not approve. Or would he?
Aristotle wrote about how every effect must have a cause, and that this is one way to go about pondering God's existence. In this kind of reasoning, God would be the ultimate Cause of all things: He would be the one who got everything going. He started the first effect, which caused the next effect, and so on. He is the Unmoved Mover who got everything else moving.
In “Blink,” there is no Unmoved Mover. The last mover moves the first mover in a circle. It is not an endless circle, however: it went around once. And that's where I have a problem. Wouldn't it either have to go around infinitely, happening over and over again, or else have an outside force breaking in at some point along the circle to get it rolling?
So you see what I meant when I said this is a lovely philosophical conundrum rather than a flaw in the story. It's more a question about how things—time, events, causation—work, rather than an action plot that uses time travel as a cheap device. Brilliant work, Moffat.