By His Bootstraps was first published in Astounding Science Fiction in October 1941 under the pseudonym Anson McDonald. The story was reprinted in Heinlein’s 1959 collection The Menace From Earth and in various subsequent anthologies. John Campbell, the editor, immediately recognised it as one of the great technical tours de force of science fiction and readers agreed. It remained, almost, the ultimate ‘‘loop in time’’ story until Heinlein outdid himself 18 years later with All You Zombies.
It is a well spun and tightly intertwined tale of time travel loops and the resultant paradoxes, involving the unpleasant Bob Wilson and visits from other iterations of himself. The story begins with him writing his philosophy thesis on the impossibility of time travel, as in terms first used by Immanuel Kant, time, is only empirically real and does not exist independently among things in themselves. Then suddenly, a Time-Gate opens and our narrator is visited by two different editions of himself , a Joe and then a Diktor, both from the future with conflicting views of what he can do in this future. Bob Wilson goes through loop after time loop and experiences the same event but from multiple perspectives, but they are crucially his personal perspective alone. His final destination is a far future world reminiscent of that portrayed in The Time Machine where humanity has become similar to the Eloi not through any process of social Darwinianism as in H.G. Wells, but by a different fictional mechanism—long-vanished, alien masters. This is where Bob intends to confront the older man he met on a previous visit to the future (Diktor), but it transpires that this older man is actually himself and his future is (and always has been) locked in. Bob manipulates the controls of the Time-Gate and arrives at a place that is 10 years earlier than Diktor’s ”now” and establishes himself as Diktor. It is not until these 10 years have elapsed and there is no sign of ‘Diktor’ that Bob/Joe/Diktor realises that all of his actions whether intentional or unintentional have created the very future he was trying to alter: a predestination paradox.
Bob Wilson does indeed set himself up ‘‘by his bootstraps’’ – his various editions all interact with each other to produce the end result. Although Bob Wilson is repeatedly looped in time, he does, by implication, exit the tangle of loops in time by the end as he becomes the only remnant of human society much like the Time Traveler in The Time Machine. However, there is another paradox, an information paradox. When Wilson travels to the future he is given a notebook by the older man (Diktor) who Wilson is as yet unaware is himself. This notebook contains the vocabulary of the language spoken in the future. Wilson learns the language, but the book wears out and he copies it to another notebook when returning to the present. So, Wilson is both the person who learnt the language in the future, compiled the lexicon and then copied it when he returned to the past and then was given this book by himself before he had become Diktor. So: who wrote the notebook? Well Diktor wrote it but how could he if Wilson hadn’t yet learnt the language?! An ontological paradox. There is no starting point and no end point, a true circle in time. Also known as, if you prefer modern scientific terminology an example of the Novikov Self-Consistency Principle. In fact, Bob Wilson himself realises that there is something ”peculiar” about this in his own story.
While the paradox in Heinlein’s story does produce a consistent account of Bob/Joe/Diktor’s timeline one massive problem with this ontological conundrum is an apparent violation of the Law of Causality. We are no longer able to say that a past ’cause’ led to a future ‘event’, as the event such as the creation of the notebook may equally have been created in the future before leading to its cause in the past. If the past, present and future are all equal then the ‘origin’ of an event becomes meaningless, in time travel stories anyway.
A similar ”peculiar” ontological paradox arises in the 1980 movie Somewhere In Time with Christopher Reeve and Jane Seymour. The film is an adaptation of the science-fiction novel Bid Time Return (1975) by Richard Matheson. A young college student (Reeve) is celebrating the debut of his play when an elderly woman (Susan French) places a pocket watch into his hands and pleads: ”Come back to me.” He does not recognise her and she dies soon after.
Eight years later whilst on a break from writing, Richard (Reeve) chances upon a photograph of the mysterious elderly woman when she was much younger and is captivated by her. He discovers a book on time travel among her possessions and determines to meet her by travelling back in time to 1912. Visiting the writer of this book, a Dr. Finney he learns that it may be possible to return to the past through self-hypnosis but that it may well cause serious physical harm to the body. He immerses himself in artifacts and accoutrements from the relevant period and through sheer will power manages to travel to 1912 where he meets her and they fall in love. However, during one liaison, Elise asks the time and Richard duly obliges with the pocket watch she gave him but having grabbed his jacket he finds inside a coin from 1972 and with that fatal anachronism he is immediately returned to his own time leaving her with the now infamous pocket watch. So here is our information or ontological paradox: where did the pocket watch come from?! A simple question taken at face value but in time travel nothing is simple.
If we consider for a moment the clock’s worldline ( the path it traces in both space and time, providing its history) we know it was given to Richard in 1972 and taken back with him to 1912, where it was left when he disappeared back into the future, then stayed with Elise until she gave it to Richard in 1972. Such worldlines are called closed timelike curves or CTC’s for short. So where did the watch originate?! In 1912? Yes & No. Yes because Richard leaves the watch and No because Elise did not have the watch until Richard arrived from 1972. In 1972? Yes & No. Yes because Elise has the watch given to her in 1912 and No because Richard hasn’t given her the watch yet! Just like the notebook in Heinlein’s story it implies that the watch exists without ever having been created or rather without a beginning or an end the watch seems to have appeared through magic or sorcery, creatio ex nihilo.
In 1992 the Russian time travel pioneer Igor Novikov (whom I referenced earlier) and his colleague Andrei Lossev published a now iconic paper in Classical and Quantum Gravity. This paper was primarily concerned with CTC’s and a scientific discussion of the paradoxical objects that exist there, like the pocket watch in Somewhere in Time. They decided to call these objects jinn (or djinn) after the Arabic word for a spirit or genie. Perfect choice as who does not remember Aladdin and the rubbing of the magic lamp to release the timeless genie from its captivity. Yet the watch somehow is immune to the rubbing and wear and tear that must have occurred in the intervening 60 years when the watch is given to Seymour and then kept by her until the day she returns it to Reeve in the future and the CTC repeats. This leads us to the next problem with time travel as Novikov and Lossev discussed.
Entropy?! The watch in 1972 is in the same pristine condition as the same watch in 1912. According to the famous Second Law of Thermodynamics the watch (or the particles that form this watch) should have become disordered and the watch started to lose structural integrity and basically age, but it has not. As time unfolds in our Universe things become more chaotic and less ordered. Hopefully the chart above will help.
An object, any object or jinn, trapped in a causal time loop would continue to age and eventually fall apart creating a contradiction. It also raises the question of identity and will involve another paradox much discussed by the ancients. The Ship of Theseus paradox is described in Plutarch’s Life of Theseus. The ship that had brought Theseus back from Crete after he had killed The Minotaur was kept in the harbour as a memorial to their greatest Athenian hero. But, after a while the sail became torn and the oars and planks became rotten and these parts had to be replaced. Until pretty much every component comprising the ship had been replaced. So was this still the Ship of Theseus?
It was discussed at great length by the ancients. Heraclitus held that it was not the same ship and his answer gave rise to his famous saying, ”one cannot step into the same river twice” meaning that you nor I are the same person or same composition as we were yesterday. It is not the same river and so it is not the same ship. Aristotle thought that it was the same ship as it had only been affected by insubstantial changes. In his analysis he distinguished between accidental and essential features of objects. What does it matter if the accidental features, like the planks and oars, are changed? The essential feature, that of the ship being able to sail, is still intact. We are left to conclude therefore that The Ship of Theseus (and the watch in the film), both is and is not a real object and that we have another paradox created by time travel.
The knowledge (the notebook) in By His Bootstraps travels from future to past and back without having an actual causal origin external to the CTC. It is ”peculiar” as the narrator notices but it doesn’t violate any logical rules or laws of nature in our universe. But the watch similarly uncreated in Somewhere in Time does violate our laws of nature, for its existence in time on a CTC involves wear that cannot be reversed by travelling from the future to the past. The watch arriving in the past cannot be the same watch that left the future since the watch in the past is changed by the operation of entropy. If time travel makes that watch possible, then travelling in time is impossible and Stephen Hawking is right again. But, there are still many, many, great time travelling stories to read and to write about.