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Pathways to Philosophy

Glass House Philosopher


to David Gerrold's The Man Who Folded Himself

by Geoffrey Klempner

Die Tatsachen im logischen Raum sind die Welt

'The facts in logical space are the world'

Wittgenstein Tractatus Logico-Philosophicus 1.13

Once upon a time, travelling to the past or future was a simple affair. "There is no difference between time and any of the three dimensions of space, except that our consciousness moves along it," H.G. Wells' Time Traveller tells his sceptical diner guests. We are carried along with the flow of time, like passengers on a train with no doors which will never stop, gazing at the scenery passing by. A time machine allows you to get off the train. For the time traveller, time is just another kind of "space".

It intrigues me to think that as I tentatively put down these words there is, somewhere in the not-too distant future, the finished version of this Afterword waiting to be e-mailed to the publishers. Though the blank page holds no terror for me, I would certainly be tempted — if I had Dan's timebelt — to sneak a peek at what I wrote. Better still, wait until The Man Who Folded Himself is in the bookshops, then I know I will be looking at the final version.

Now I imagine I am back in the present, holding the book in my hands. I don't have to write another word because it has already been written. I can just copy it out. But if my piece is already written, who (or what?) did all the hard work of actually writing it?

This is too much for my brain to cope with. Let's try something simpler. There isn't anything in the novel quite simple enough for our purposes (you'll see why), so I am going to compose a miniature time travel story of my own:

You wake up one morning to find Dan's timebelt on the table next to your bed. (You recognize it immediately because you have just finished reading the novel.) "This is great," you think. "I'm going to take a short hop to yesterday evening to warn myself." But then it dawns on you that you can't do that because you didn't. No scribbled note was found, your double did not mysteriously appear at the front door. You feel defiant. "But I can, and I will!" So you go.

Now, we have to tell the story all over again:

Last night, your double mysteriously appeared at the front door. "Guess what, tomorrow morning you are going to be the proud owner of one of these. Take care how you use it!" Before you have time to blurt out a reply, your double taps the timebelt and is gone. Next morning, the prophecy turns out to be true. Now you think, "I have to go to yesterday evening to warn myself." But why bother? You already know. So you don't go.


The basic ground rule for writing any piece of fiction is that the story should add up. The plot should be consistent. It should make logical sense. Sometimes a writer breaks the consistency rule, and sometimes an inattentive reader fails to notice. But that's really not a satisfactory state of affairs. So the question we have to ask is: Is the story about the timebelt on the bedside table consistent? Or, more precisely: Is there a way to interpret what happened that gives the story the required coherence?

Some readers' imaginations may stretch further than others. But sometimes it can stretch too far. One of my teachers once jokingly remarked that his imagination was better than mine because he could imagine a square circle.

"Want to know what it looks like?"

"I give up, Sir. Tell me."

"A bit fuzzy round the edges!"

When the plot of a story or novel is inconsistent, our mental picture goes fuzzy. We see one part, then another, but, try as we might, we cannot connect the two.

There is a way to make the story about the bedside table coherent. But to do that we first need to go back in time to get some help from one of the foremost thinkers of the ancient world.

Two and a half thousand years ago, Aristotle asked the following question: In what sense can we regard the statement, "There will be a sea battle tomorrow" as true or false at the time at which it is uttered? (The ancient Greeks were always having sea battles.) If it is a fact now that a sea battle takes place tomorrow then we are condemned to fatalism. The same result follows if it is a fact now that a sea battle will not take place tomorrow. Either way, the future is all laid out. Thinking and deciding are mere illusions. That is just how things are for passengers on the time train I mentioned earlier.

Aristotle won't accept this. His conclusion agrees with common sense: that while the past is necessarily what it is — what is done is done — the future is contingent. There is a possible future where a sea battle takes place and another possible future in which it does not take place. So there is still scope for human deliberation, and fatalism is avoided.

There are two separate versions of my story about the timebelt, taking place in two alternative universes, or different possible futures. And each version of the story branches out into two more possible futures. Let's run through them all:

A1 I did not go back to the past to warn myself and I decide not to warn myself.

A2 I did not go back to the past to warn myself, but, despite this, I decide to warn myself.

B1 I did go back to the past to warn myself and I decide to warn myself.

B2 I did go back to the past to warn myself, but, despite this, I decide not to warn myself.

Now we can see that Aristotle's theory of future contingency isn't enough to save the coherence of the story. In either version, A or B, one possible choice I can make is that I go back to change my own past.

So we have to turn Aristotle's theory on its head and apply it to the past too. What is done is not necessarily done. It can be undone. But how? In the first version of the story, I remember distinctly that I did not warn myself. If I go back into the past now to face the 'myself' of yesterday, then the person who receives the warning cannot be me. He cannot exist in my past, but only in an alternative past that comes into existence the moment I double tap the button on my timebelt.

It is sobering to realize that you cannot change the past one iota. All you can do is bring into existence new versions of the history of the universe where the past is different from what it in fact was. You cannot use the timebelt to stop the Holocaust by murdering Hitler when he was 20, you can only create a universe where the Holocaust never happened. You cannot save the life of President Kennedy, you can only save the life of Kennedy's double. You can't prevent the actual horror and suffering of September 11th. You can only distance yourself from it, by taking yourself away to another world where the Twin Towers still stand.

It takes Dan quite a while to grasp the full implications of this idea. Like H.G. Wells' hero struggling to understand the ways of the Eloi and the Morlocks, Dan — the reader too! — struggles to catch up with the plot. He tries one unsatisfactory explanation, then another, and it is not until nearly half way through the novel that light finally begins to dawn: "When you use the timebelt, you aren't really jumping through time, that's the illusion; what you're actually doing is leaving one timestream and jumping to — maybe even creating — another."


Let us leave the subjective standpoint of the time traveller for a moment and consider the objective view. For if the events we are describing are consistent, then there must be a way to tell the same story from the point of view of an external observer.

Imagine that you are an all-seeing deity, not quite as malevolent as Descartes' Evil Demon, but not quite as beneficent as Descartes' Perfect Being either. Before you is spread the entire history of Creation, from the Big Bang to the Big Crunch. Or possibly an infinite series of bangs and crunches stretching in both directions (choose your favourite cosmological theory). Everything is held together by physical laws, laws which state that 'if A happens then B will happen'. A mixture of oxygen and hydrogen gas when ignited combines to form water. People who drink cyanide generally die. Nothing comes from nothing: whatever happens after is the result of what happened before, according to the universal, immutable laws of physics.

Perhaps out of a sense of mischief — or maybe just because you like to experiment — you decide to introduce a new variable into the equation. You make an exception to the laws of physics, or rather you add a new super-law, and let human ingenuity do the rest. That is Dan's timebelt.

In the time travel universe, or universe of universes, we cannot allow that anything goes. For that would lead to inconsistency. There must be rules or limits which determine what can or cannot happen. The laws which govern the timebelt are not the laws of physics as we know them (of course, it could turn out that we are wrong about that!) but they are laws nonetheless: there is no logical reason why the laws of physics and the laws governing the timebelt should not be compatible. The timebelt is no magical device but has inner workings which operate in an intelligible way. Otherwise the time traveller would never know for sure where he or she was going.

Anyone who has ever used a word processor can pick up the idea very easily. Say, you're writing a paper and you're unhappy with what you said in paragraph three. So you cut out a sentence and insert it into paragraph four. Now your argument begins to look convincing. However, to accommodate the change you need to say other things too. Out go paragraphs five and six, and in their place something entirely different. You read through the revised version and decide that another sentence needs to be moved. And so on, until you are satisfied that the whole piece has the quality you are aiming for. "I am the artist of time," realizes Dan.

When Dan puts on the timebelt, it is as if he acquires the power to cut himself out of the timestream, out of the text of human history, and paste his momentary self into another point in time in a hitherto identical universe. Simple enough, until you realize that the process can be iterated, without end. The process is what mathematicians call recursion. You apply a rule or process to a product of that same rule or process, over and over.

From the point of view of our mischievous deity, the result is a dizzyingly complex structure of possible histories of the universe, branching out, spiralling, looping back. No individual gets to see the whole structure. From any given point, certain histories are accessible, others inaccessible. Tragically, for Dan, worlds that were once accessible cease to be accessible. A timebelt does not give you the power to turn back the clock of your own life.


What kind of thing must time be, if all this is possible? What kind of thing is a person or 'I', that can move from one world, one history of the universe to another, miraculously preserving the invisible thread of self-identity?

I don't know what kind of thing time would be in a time travel universe, because I don't know what time is. I don't understand where the past goes. I don't know how to define what makes now different from all other 'nows'. Dan's story is intriguing, gripping, but the reason is not merely because time travel is an exotic idea. "What is time?" is a mind-boggling question. So is the question, "What is 'I'?"

There is one point in the novel where Dan, or rather a version of Dan, succumbs to paranoid schizophrenia. Dan's first thought is, "If there are an infinite number of Dans, then each one thinks he is choosing his own course. But that isn't so. Each one is only playing out his preordained instructions — excising, altering, and designing his timestream to fit his psychological template and following his emotional programming to its illogical extreme." But then later, "It bothers me — this me. I need to know that there is some important reason for my existence. There must be something special about me." There is such a reason, Dan finally realizes as he slips into madness: "I am God".

Like the problem of time, the nature of "I" is a problem for us in the actual world, not just for Dan in the world of the novel. What makes the problem so acute for Dan is that there are so many versions of Dan around. But that is a point of mere detail. Each of us, when we say "I" and point to ourselves realize that all our physical and mental qualities put together are not enough to make me "I". An exact copy of me, thought for thought, molecule for molecule, would not be "I". Then what is sufficient to make me "I"? What is the extra ingredient for individuality? I don't know any thinker who has given a satisfactory answer to that question.

Further Reading

The reader interested in exploring further the themes discussed in the Afterword should consult the following:

Aristotle De Interpretatione. E.M. Edghill trans. (In Gale pp. 179—182)

Descartes Meditations on First Philosophy 1641 (several editions)

Gale, R. ed. The Philosophy of Time. Macmillan 1968

Le Poidevin, R. and MacBeath, M. eds. The Philosophy of Time. Oxford University Press 1993

Lewis, D. "The Paradoxes of Time Travel". (In Le Poidevin pp. 134—146)

Wells, H.G. The Time Machine 1895 (downloadable e-text)

Wittgenstein, L. Tractatus Logico-Philosophicus. Pears, D.F. and McGuinness B.F. trans. Routledge 1961

[I would like to thank Steven Ravett Brown, Tom Farrow, Hubertus Fremerey, Rune Froseth, Adriano Lima and Kenneth Stern who responded helpfully to questions about time travel which I posted on the Pathways web site.]

© Geoffrey Klempner 2003

This essay was commissioned by BenBella Books as an afterword to the new edition of the 70's science fiction time travel classic The Man Who Folded Himself by David Gerrold, published 2003.