Time Travel. A History

I don’t want to talk about time travel shit, because we’ll start talking about it and then we’ll be here all day talking about it and making diagrams with straws.

—Rian Johnson (2012)

A MAN SITS in a locked room with his cigarettes, pots of coffee, and a typewriter. He knows all about time. He even knows about time travel. He is Bob Wilson, a Ph.D. candidate struggling to complete his thesis, “An Investigation into Certain Mathematical Aspects of a Rigor of Metaphysics.” Case in point: “the concept ‘Time Travel.’ ” He types, “Time travel may be imagined and its necessities may be formulated under any and all theories of time, formulae which resolve the paradoxes of each theory.” More quasiphilosophical handwaving. “Duration is an attribute of consciousness and not of the plenum. It has no Ding an Sich.”

Behind him he hears a voice. “Don’t bother with it,” the voice says. “It’s a lot of utter hogwash anyway.” Bob turns to see “a chap about the same size as himself and much the same age”—or maybe just a bit older, with a three-day beard and a black eye and a swollen upper lip. The chap has apparently emerged from a hole hanging in the air: “a great disk of nothing, of the color one sees when the eyes are shut tight.” He opens a cupboard, finds the bottle, and helps himself to Bob’s gin. He looks vaguely familiar and he certainly knows his way around. “Just call me Joe,” he says.

We see where this is going—we, people of the future, the time-savvy twenty-first century—but this story is taking place in 1941, and poor Bob is slow to catch on.

Bob’s visitor explains that the hole in the air is a Time Gate. “Time flows along side by side on each side of the Gate….You can walk into the future just by stepping through that circle.” Joe wants Bob to walk through the Gate into the future. Bob doubts whether this is a good idea. As they discuss it, passing the gin bottle back and forth, a third man materializes. He bears a certain family resemblance to Bob and Joe. He does not want Bob to enter the gate. Now it’s a committee. The phone rings: a fourth man, checking on everyone’s progress.

Speculative philosophers and pulp readers had predicted this. In time travel, you can meet yourself. It’s finally happening, and it’s happening every which way. Before we are done we will have five protagonists, and they are all Bob. The author was Bob, too: Robert Anson Heinlein, writing under one of his several pen names, Anson MacDonald. His original title was “Bob’s Busy Day”; the pulp magazine Astounding Science Fiction published it in October 1941 as “By His Bootstraps.” It was the most intricate, complex, carefully plotted exercise in time travel to date.

No grandfathers die, no future mothers are impregnated, but wisecracks are exchanged and punches thrown. Scenes are narrated by one Bob and then reprised from the point of view of an older, more knowing Bob. You might expect “Joe” to remember his first encounter with Bob, but he finds the changed perspective confusing. Recognition only dawns slowly. The Bobs have to climb a ladder of growing self-awareness. To unravel the timeline we need a Minkowskiish diagram. Heinlein drew one for himself while drafting the story.

Credit 5.1

Really, of course, there are multiple timelines in play. Besides the Bobs’, there is the reader’s: the arc of the narrative. Our point of view is the one that matters. The author coaxes us gently along. He says of his poor hero, “He knew that he had about as much chance of understanding such problems as a collie has of understanding how dog food gets into cans.”

Robert Heinlein came from Butler, Missouri, in the heart of the Bible Belt, and made his way to Southern California by way of the U.S. Navy, in which he served between the wars as a midshipman and sometime radio officer aboard the Lexington, one of the first aircraft carriers. He considered himself well skilled in ordnance and fire control, but after a collapse from pneumonia he was discharged as disabled. He wrote his first story in 1939 for a contest. Astounding Science Fiction paid him seventy dollars for it, and he began pounding the typewriter; he quickly became one of the pulps’ most prolific and original writers. “By His Bootstraps” was one of more than twenty stories and short novels he published under various names in the next two years alone.

That first prizewinning story, “Life-Line,” began in a familiar way: a mysterious man of science explains to a group of skeptical listeners that time is, still and always, the fourth dimension. “Maybe you believe it, perhaps not,” he says. “It has been said so many times that it has ceased to have any meaning. It is simply a cliché that windbags use to impress fools.” He asks them now to take it literally and to visualize the shape of a human being in four-dimensional spacetime. What is a human being? A spacetime entity measurable on four axes.

In time, there stretches behind you more of this space-time event, reaching to, perhaps, 1905, of which we see a cross section here at right angles to the time axis, and as thick as the present. At the far end is a baby, smelling of sour milk and drooling its breakfast on its bib. At the other end lies, perhaps, an old man some place in the 1980s. Imagine this space-time event…as a long pink worm, continuous through the years.

A long pink worm. Slowly and gingerly, the culture was digesting the space-time continuum. The easy bits no longer needed quite so much explaining, so some nuances could be revealed.

The fun of “By His Bootstraps” lies in the comic encounters of the Bobs; it’s a one-man farce times five, with misplaced hats, a confused and irate girlfriend (the word two-timing has never been so apt), and, with the Time Gate, the sci-fi equivalent of comically timed slamming doors. The hat is tossed and found and lost again until it seems to be multiplying like rabbits. Bob gets drunk with Bob. Bob recoils at the sight of drunken Bob, and Bob calls Bob some choice names. But Heinlein also takes some pains with the science. Or the philosophy. The eldest and wisest of the Bobs, living thirty thousand years in the future, tells one of his past selves, “Causation in a plenum need not be and is not limited by a man’s perception of duration.” Young Bob thinks about this and offers a comeback: “Just a second. How about entropy? You can’t get around entropy.” And so on. Examined closely, this gab is as hollow as the painted storefronts on the set of a Western.

Heinlein himself apparently didn’t think much of the story at first and was surprised when the magazine’s influential editor, John W. Campbell, assured him it was something special. In its way, it begins to grapple with two philosophical difficulties that arise when people start looping back through spacetime. One is the problem of who they are—the continuity of the self, let’s call it. It’s all well and good to talk about Bob Number One and Bob Number Two and so on, but the diligent narrator finds language ill equipped to keep everyone sorted: “His earlier self faced him, pointedly ignoring the presence of the third copy.” Suddenly English doesn’t have enough pronouns.

His memory had not prepared him for who the third party would turn out to be.

He opened his eyes to find that his other self, the drunk one, was addressing the latest edition.

Not only does Bob gaze upon himself—worse, he doesn’t like the way he looks: “Wilson decided he did not like the chap’s face.” (But we don’t need time travel to reproduce that experience. We have mirrors.)

What is the self? A question for the twentieth century to ponder, from Freud to Hofstadter and Dennett with detours through Lacan, and time travel provides some of the more profound variations on the theme. We have split personalities and alter egos galore. We have learned to doubt whether we are our younger selves, whether we will be the same person when we next look. The literature of time travel (though Bob Heinlein, in 1941, would not have dreamt of calling his work literature)^*1 begins to offer a way into questions that might otherwise belong to philosophers. It looks at them viscerally and naïvely—as it were, nakedly.

If you’re having a conversation with someone, can that person be you? When you reach out and touch someone, is it a different person, by definition? Can you have memories of a conversation while you’re speaking the very words?

Wilson’s head started to ache again. “Don’t do that,” he pleaded. “Don’t refer to that guy as if he were me. This is me, standing here.”

“Have it your own way. That is the man you were. You remember the things that are about to happen to him, don’t you?”

He arrives at a conclusion: “The ego was himself. Self is self, an unproved and unprovable first statement, directly experienced.” Henri Bergson would have appreciated this story.

He thought of a way to state it: Ego is the point of consciousness, the latest term in a continuously expanding series along the line of memory duration….He would have to try to formulate it mathematically before he could trust it. Verbal language had such queer booby traps in it.

He accepts the fact (because he remembers) that his earlier selves had also felt themselves to be the one and only integrated and continuous being, Bob Wilson. But that must be an illusion. In a four-dimensional continuum each event is an absolute individual, with its own spacetime coordinates. “By sheer necessity he was forced to expand the principle of nonidentity—‘Nothing is identical with anything else, not even with itself’—to include the ego. The Bob Wilson of now is not the Bob Wilson he had been ten minutes ago. Each was a discrete section of a four-dimensional process.” All these Bobs—no more one and the same than the slices of bread in a loaf. And yet, they have continuity of memory, “a memory track that ran through all of them.” He recalls something about Descartes. If we know anything about philosophy we know this: cogito ergo sum. We all feel that. It is the defining illusion of Homo sapiens.

As readers, how can we help but understand Bob as a unified self? We have lived with him through all the twists of his timeline. The self is the story he tells.

—

WE REACH (and it won’t be the last time) the problem of free will. This was the second of the philosophical difficulties that Heinlein decided to explore as his narrative proceeded. Or perhaps I should say, found himself exploring, willy-nilly. He had no choice. When you send Bob back in time to meet his earlier self and relive an episode from his newer, wiser point of view, it is inevitable that Bob will ask: Can’t I do it differently this time?

Then we loop again, and now Bob Three, older and wiser still, disagrees with Bob Two about what Bob One ought to do. He presumes that he, or they, have a choice. Will the earlier Bob defer to the superior wisdom of his later self? Hardly. He still needs to give one self a black eye and push the other self through the Time Gate.

The reader sees the whole picture—from above, so to speak—well before Bob does. Bob tries using the Time Gate as a window into spacetime, but the controls are hard to manage. Sometimes he sees, or senses, “flitting shadows which might be human beings.” We know they are his own shadows, flickering on the cave wall. Bobs one and all are striving to fulfill their own destiny. The paradox, if it is a paradox, is that they have to work so hard, even as they gradually realize that their looping travails are foreordained. There is no escape from the track they are on. As Bob hears himself reciting words he has already spoken, he tries feebly to rewrite the script. “You’re a free agent,” he tells himself. “You want to recite a nursery rhyme—go ahead and do it…and break this vicious circle.” Yet just at that moment he can’t think of a nursery rhyme. His lines have been written for him. He can’t get off the treadmill.

“But that’s impossible!” he cries. “You’re telling me that I did something because I was going to do something.”

“Well, didn’t you?” he calmly retorts. “You were there.”

Young Bob still doesn’t like it. “You would have me believe that causation can be completely circular.” And Old Bob, despite all his hard-won knowledge, never stops working to fulfill his destiny. He does not wait for his earlier selves to play their roles; he manipulates them urgently. The narrator says: “Everyone makes plans to provide for their future. He was about to provide for his past.” Taken all in all, this story is a snake pushing its own tail while musing about whether the effort is necessary.

The author, churning out stories on his manual typewriter to pay the bills in Southern California, trying to make his plots plausible and his characters convincing, has his own problem with free will. He makes his people into puppets, the strings flickering in and out of our sight. Their own view is foreshortened. Only the omniscient author, with his penciled diagrams, sees everything at once. We readers are caught up in the story, remembering the past, anticipating the future; we are mortals, for whom now means now.

It’s not easy to get past that, in reading stories or in living our lives. As Heinlein puts it, we must make “a strong and subtle intellectual effort to think other than in durational terms, to take an eternal viewpoint.” Free will cannot be easily dismissed, because we experience it directly. We make choices. No philosopher has yet sat down in a restaurant and told the waiter, “Just bring me whatever the universe has preordained.” Then again, Einstein said that he could “will” himself to light his pipe without feeling particularly free. He liked to quote Schopenhauer: Der Mensch kann wohl tun, was er will; aber er kann nicht wollen, was er will. Man can do what he will, but he cannot will what he wills.

The free will problem was a sleeping giant and, without particularly meaning to, Einstein and Minkowski had prodded it awake. How literally were their followers to take the space-time continuum—the “block universe,” fixed for eternity, with our blinkered three-dimensional consciousnesses moving through it? “Is the future all settled beforehand, and only waiting to be ‘pushed through’ into our three-dimensional ken?” asked Oliver Lodge, the British physicist and radio pioneer in 1920. “Is there no element of contingency? No free will?” He begged for a sort of modesty. “I am talking geometry, not theology, and it would be a stupid mistake to pretend to decide questions of high reality by aid of mere groping analogies and mathematical analysis….The human race has not been in existence very long; it began its scientific studies very recently; it is still scraping on the surface of things, the three-dimensional surface of things.” We may say the same, a century later.

—

PHILOSOPHERS DID NOT NEED the space-time continuum to tell them that there were problems about free will. As soon as the rules of logic were added to the human tool kit, the ancients found themselves capable of constructing the most amusing puzzles. Human language switches between past and future with a simple change of tense, and this can trap the unwary.

“For what is and what has come about, then, it is necessary that affirmation, or negation, should be true or false,” Aristotle said. In other words, statements about the present and statements about the past are either true or false. Consider the proposition There was a sea battle yesterday. True or false. There is nothing in between. So it is natural to consider whether this applies to statements about the future. There will be a sea battle tomorrow. By Saturday this will be true or false, but must it be either true or false now? Put in terms of language and logic, these propositions look identical, so the same rules should apply. There will be a sea battle tomorrow. If it’s not true or false, what else is there?

Aristotle remained unconvinced. He carved out an exception for propositions about the future. Where the future is concerned, he felt logic needed room for another state of things: call it indeterminate, contingent, unfixed, unknown, up for grabs…The modern philosopher finds this clumsy.

By the weekend, there will have been a sea battle. Not every language has a future perfect progressive tense built in; when your language does, it tends to feel natural. Either there will have been a sea battle or there won’t. When the time comes, we’ll know which. It will seem to have been inevitable. In this way, language and logic tend to suggest an eternalist view, the Universe Rigid, the view that gained solidity with the arrival of clockwork physical laws as revealed by Newton and Laplace. The block-universe package was wrapped and sealed, seemingly, in the four-dimensional space-time continuum. The new physics profoundly influenced philosophers, whether they acknowledged it or not. It freed them from the common intuitive sensation that past and future are quite different. It freed philosophers, that is, while imprisoning the rest of us. “Past and future must be acknowledged to be as real as the present,” wrote Bertrand Russell in 1926, “and a certain emancipation from slavery to time is essential to philosophic thought.”^*2 A fatalist says: Everything that happens had to happen. Q.E.D.

Donald C. Williams, a realist from California, picked up that thread at midcentury with a paper on “The Sea Fight Tomorrow.” His brand of realism was four-dimensional—fully modern, in other words. He asserted “the view of the world, or the manner of speaking about it” (a nice distinction, so easily forgotten),

which treats the totality of being, of facts, or of events as spread out eternally in the dimension of time as well as the dimension of space. Future events and past events are by no means present events, but in a clear and important sense they do exist, now and forever, as rounded and definite articles of the world’s furniture.

In the 1960s, the sea battle of tomorrow got a new life in the journals of philosophy. An argument raged over the logic of fatalism, and a milestone in the debate was the essay “Fatalism” by Richard Taylor, a metaphysician and beekeeper at Brown University. “A fatalist,” he wrote, “thinks of the future in the manner in which we all think of the past.” Fatalists take both past and future as given, and equally so. They may get this view from religion or, lately, from science:

Without bringing God into the picture, one might suppose that everything happens in accordance with invariable laws, that whatever happens in the world at any future time is the only thing that can then happen, given that certain other things were happening just before, and that these, in turn, are the only things that can happen at that time, given the total state of the world just before then, and so on, so that again, there is nothing left for us to do about it.

Taylor proposed to prove fatalism entirely by philosophical reasoning, “without recourse to any theology or physics.” He used symbolic logic, representing the various statements about the sea battle in terms of P and P′ and Q and Q′. All he needed were “certain presuppositions made almost universally in contemporary philosophy.” Something had to give: either fatalism or the rules of logic. A philosophy battle ensued. One of Taylor’s presuppositions was not as evident to everyone else: “that time is not by itself ‘efficacious’; that is, that the mere passage of time does not augment or diminish the capacities of anything.” In other words, time itself is not an agent of change; more of an innocent bystander. Time doesn’t do anything. (“What is a mere passage of time” retorted one of his critics. “Could time possibly pass without something, somewhere, changing—without the tick of a clock, the movement of a planet, the twitch of a muscle, or the sight of a flash?”)

Two decades later, at Amherst College, an undergraduate philosophy student named David Foster Wallace, himself the son of a professional philosopher, grew obsessed with this nettlesome debate, “the famous and infamous Taylor argument.” He wrote to a friend, “If you read the Taylor literature, it’s really ulcer-city.” He plunged in nonetheless. His obsession became his honors thesis, which might have taken its title from the imaginary Bob Wilson’s “An Investigation into Certain Mathematical Aspects of a Rigor of Metaphysics.” He drew diagrams to sort out “world-situations” and their possible “daughters” and “mothers.” Yet as much as the formal, axiomatic side of philosophy appealed to Wallace—gave him continual pleasure and satisfaction—he never accepted it without reservation. The limits of logic and the limits of language remained live issues for him.

Words represent things but the words are not the things. We know that but we can forget. Fatalism is a philosophy built out of words, and ultimately its conclusions apply to words—not necessarily to reality. When Taylor leaves work, he summons the elevator just like the rest of us, by pressing the button. He does not think to himself, Don’t worry, the elevator will follow its destiny. He may think, When I press the elevator button, it is not a free choice—it was fated. But he still goes to the trouble of doing it. He doesn’t just stand there and wait.

Of course, Taylor himself knew this full well. He can’t be refuted so easily.

A fatalist—if there is any such—thinks he cannot do anything about the future. He thinks it is not up to him what is going to happen next year, tomorrow, or the very next moment. He thinks that even his own behavior is not in the least within his power, any more than the motions of the heavenly bodies, the events of remote history, or the political developments in China. It would, accordingly, be pointless for him to deliberate about what he is going to do, for a man deliberates only about such things as he believes are within his power to do.

He added, “And we are not, in fact, ever tempted to deliberate about what we have done and left undone.”

I wonder whether Taylor had read much time-travel fiction or even, for that matter, whether he lived in the world I live in, where regret is not unknown and people do sometimes speculate about what might have been. Everywhere we look, people are pressing elevator buttons, turning doorknobs, hailing taxicabs, lifting sustenance to their lips, and begging their lovers’ favor. We act as though the future is, if not in our control, not yet settled. Nonetheless, Taylor dismissed our “subjective feelings.” We would suffer illusions of free will, because, by happenstance, we tend to know less about the future than about the past.

Many philosophers, in the years that followed, had tried to refute Taylor, but his logic proved amazingly robust. Wallace wanted to defend the common intuition “that persons as agents are capable of influencing the course of events in their world.” He plunged into the depths of symbolic logic. “Since obviously under any analysis I have to do either O or O′ (since O′ is not-O), that is, since (O ∨ O′); and since by (I-4) it is either not possible that I do O or not possible that I do O′, (∼◊O ∨ ∼◊O′), which is equivalent to (∼◊∼∼O ∨ ∼◊∼O), which is equivalent to (∼O ∨ O), we are left with (O ∨ ∼O); so that it is necessary that whatever I do, O or O′, I do necessarily, and cannot do otherwise” is a sample sentence. (“Obviously”!) In the end he defeated Taylor’s fatalism by stepping back and viewing not only the chains of symbols but also the levels of symbolic representation—viewing them, as it were, from above. Wallace distinguished between the realm of semantics and the realm of metaphysics. Considered strictly as words, he argued, Taylor’s logic may be internally valid, but it’s cheating to leap from semantic premises and arguments to a metaphysical conclusion.

“Taylor’s claim was never really that fatalism was actually ‘true,’ only that it was forced upon us by proof from certain basic logical and semantic principles,” he concluded. “If Taylor and the fatalists want to force upon us a metaphysical conclusion, they must do metaphysics, not semantics.” In metaphysics we find the doctrine of determinism—we’ve seen this before, given its perfect expression by Laplace. Determinism is this (per Wallace):

the idea that, given a precise and total state of affairs at one instant, and the physical laws that govern the causal relations between states of affairs, there is one and only one possible state of affairs that could obtain at the next instant.

Taylor takes this for granted. If X, then Y means one thing in logic. In the physical world, it means something trickier and always (we should know by now) subject to doubt. In logic, it is rigid. In physics, there is slippage. Chance has a part to play. Accidents can happen. Uncertainty is a principle. The world is more complex than any model.

Taylor was begging the question. To prove fatalism he was assuming determinism. Many physicists do that, too, even now. “Physicists like to think that all you have to do is say, ‘These are the conditions, now what happens next,’ ” said Richard Feynman. Determinism is built into so many of their formalisms, just as it is for logicians. But formalisms are just that. The physical laws are a construct, a convenience. They are not coextensive with the universe.

Was that only possible which came to pass? Having spent years in these dark waters, Wallace had done enough philosophy for a while. He had an alternative future in mind, and he chose it. “I left there,” he said later, “and I didn’t go back.”

*1 When he writes of Bob Wilson, “His was a mixed nature, half hustler, half philosopher,” Heinlein is proudly describing himself.

*2 “There is some sense, easier to feel than to state, in which time is an unimportant and superficial characteristic of reality.”