"Don't worry, it'll all make sense. I'm a professional."

It's about time I wrote this up. I have a lot of non-time travel-related praise for both of these films, but I'm going to try to stay on topic.

Bill & Ted's Excellent Adventure is the first film in the unexpectedly successful, and still one hundred percent canonical, if sadly short-lived, American reboot of Doctor Who. It's one of two films - along with Back To The Future, obviously - which forms the bedrock of what most people of my generation understand about time travel in fiction.

Excellent Adventure adopts the second-simplest model of time travel. As is well recorded, in the simplest model of time travel, time travel is completely impossible and no time travel takes place. This is the model of time travel seen in almost all works of fiction. In the second simplest model, known as "fixed history", time travel is, by whatever means, possible, but the timeline is absolutely rigid, unalterable and perfectly internally consistent. Any attempt to alter the timeline will fail somehow - or, somehow, it will turn out that the "changes" you thought you made were part of history all along.

This is a good model of time travel to use in a story where time travel is necessary to the story, but actually changing history isn't the main point of conflict/drama/stress. (Of course, if changing history is the main point of conflict/drama/stress, you can still use a fixed history model; you can explore predestination and free will and stuff. E.g. Twelve Monkeys.) Excellent Adventure isn't kicked off by some bizarre threat to the timeline or by a grandfather paradox, but by a severely doomed history report. The stakes are visibly lower, even if they're still of apocalyptic significance to our protagonists. This means we get to relax and enjoy the adventure and not ask tiresome questions like "What if I kill my own grandfather as a baby?"

In fact, in large part, time travel stories can be characterised by how they answer this question, which is implicit in all time travel stories. Excellent Adventure, if you watch carefully, answers this question by deliberately never having the characters ask it. The closest we get is when Rufus explains, pretty much to camera, "You can do anything you want." A fixed history universe is an easy, low-stress place to tell an easy, low-stress time travel story. It's simple to explain, easy to understand.

Obviously there are also a whole bunch of unique gags which become possible in this framework. Excellent Adventure does a pretty great job of exploring these possibilities, starting from the ancient classic of Bill and Ted meeting their past/future selves at the Circle K ("That conversation made more sense this time") and concluding with the series of stupidly clever causal loop traps at the police station.

*

There are a couple of other things which the film does which are pretty interesting to me.

One is Rufus' line: "No matter what you do, no matter where you go, that clock, the clock in San Dimas, is always running." This is a really succinct explanation of a fairly deep concept, which is that Bill and Ted are anchored to the "home era" in which they were born, and have to return to that era before delivering their history report. The history report is due roughly eighteen hours later, both from their perspective and from San Dimas' perspective. This mandate apparently remains in place even when - after half a day of adventures - Bill and Ted travel back in time to the Circle K and meet themselves hours earlier.

So, why can't they just adventure for subjective years and become legendarily knowledgeable historians before giving their report? What causes this "anchoring" constraint? This question is left unaddressed. But we might just as well ask why Rufus is sent back in time to rescue Bill and Ted from their apocalyptic history failure in the first place. Why him? Why then? The answer is explicit: because that's what history records, and there's just no other way for history to go down. It's immutable. Rufus' actions and words are well-recorded - probably better-recorded by him than by Bill and Ted, in fact.

So maybe there is no mysterious "anchoring" phenomenon. Maybe Bill and Ted could have done exactly what I described, were it not for historical imperative. But they didn't, so they didn't. Ultimately, it doesn't matter. Everything falls into place, history is correct, and we're all good. Once again, in this film unlike other films, we get to fall back to a relatively relaxed posture and just let events play out as they always must, instead of worrying too much about mechanics.

The other interesting thing is this astounding development:

Bill: "Can we get your dad's keys?"

Ted: "We could steal them, but he lost them two days ago."

Bill: "If only we could go back in time to when he had them and steal them then."

Ted: "Well... why can't we?"

Bill: "Because we don't got time!"

Ted: "We could do it after the report!"

Bill: "Ted, good thinking dude! After the report we'll time travel back to two days ago, steal your dad's keys and leave them here!"

Ted: "Where?"

Bill: "I don't know. How about behind that sign? That way, when we get here now, they'll be waiting for us." [picks them up] "See?"

Ted: "Whoa, yeah! So, after the report, we can't forget to do this, otherwise it won't happen. ...But it did happen! Hey, it was me who stole my dad's keys!"

There is a substantial body of time travel stories, taking place in fixed history universes, in which causal loops take place. A causal loop is a sequence of events, each causing the next, but with no origin point, no infinite series of causes backtracking to the Big Bang.

You're locked in a cell. Mysteriously, the key to the door arrives in the cell with you. You use the key to escape. Later, you steal a time machine - you use it to send the key back to yourself in the cell. So where did the key come from? Who cut it? How come it fit the lock?

This is an extreme example; it's not often that a single object forms a concrete loop in this way. A weaker loop would be: You're locked in a cell. Mysteriously, the key to the door arrives in the cell with you. You use the key to escape. Later, you find the prison warden and steal a time machine and the original cell key. You send the newly stolen key back to yourself. Now the key is no longer a physical loop, and has a well-defined origin and purpose for existing. But still, why did it appear in your cell? It appeared because you sent it to yourself; but you were only able to send it to yourself because it appeared. Although there's no physical loop, we do have a loop of causes. And where did the loop itself come from?

Both of these examples are problematic because they are dissatisfying. You get out of jail free due to dumb luck. If this loop has no cause, how come it worked so clearly in your favour? Where are all the other causeless, pointless loops?

The film Los Cronocrímenes - which I probably won't be writing up separately - turns its protagonist from fairly ambivalent husband into - well, spoiler alert, a terrible human being. This happens because he witnesses an anonymous, disguised individual doing certain things... then, he (the protagonist) is unexpectedly looped around in time and discovers that he is the masked individual, with no choice but to somewhat reluctantly follow through. By the end of the film, this man is a terrible man. Why, then, is he a terrible man? Where did this come from? Was this capability already there in the character, or was it put there by the time machine, or what? He did things because he saw himself do things because he did things. There's no point of origin for it. Other than, inevitably, the writer, who dwells out here in time-travel-free, strictly causal reality, and that doesn't count.

My point is that causal loops in fiction are more often than not stumbled into by the characters; concocted by writers and then deliberately left as neat, pointless questions to ask at the pub later. Time travel stories are left with big, floating question marks, to which the only possible answer is "mu".

Bill & Ted's Excellent Adventure is not like this.

In the sequence above, Bill and Ted, individuals who are well-meaning and cheerful with admittedly broad vocabularies, but firmly established as dunces, somehow work out how to construct causal loops. Not just construct them deliberately, but construct them in a way which is favourable to them. There is almost a visible flash when Bill gets the idea - this is the event which causes the loop to come into existence. Notice, most critically, that this happens before he even starts looking for the keys, not after he finds them!

This always made much more sense to me - that there would be a spark at some point along the loop, some sort of injection of energy or effort of will which kicked it all off, someone who decided one day: "What's needed here is a causal loop." Bill and Ted realise that just because they are locked inside a universe no part of whose history can ever be changed, doesn't mean that every part of history is known. Those gaps in their knowledge - Exactly where did those keys go? Who has visited this police station before we did today? - can be exploited, rigged in their favour.

And just look how well the whole concept is explained. By virtue of being dunces - and not just one dunce, two dunces who are able to talk to one another - the characters are able to communicate fairly complex concepts in relatively simple language, while simultaneously communicating the same to the viewers. At one end of this spectrum is a film like Primer where the characters are superintelligent and never slow down for anybody's benefit, the viewer's or each other's. Meanwhile at the other end, Bill and Ted lay it out in simple terms which anybody can understand. It's masterful. What's happening here is education.

You're locked in a cell. You decide to summon the door key into existence, through deliberate focus. You devote some energy to cause the key-shaped loop to form ahead of you in time, where you can reach out and take it. This far more satisfying than dumb luck. It means you, Bill and Ted, have agency, and are using your resources and recently acquired knowledge to your advantage. It demonstrates that you are learning.

Admittedly, in this first example, the idea of key theft does seem to loop on itself, inspiring Bill with his idea. Similar objections can be levelled at the tape recording stunt and the fax machine trick - the ideas to make the tape recording and send the fax obviously come from hearing the tape recording and receiving the fax respectively. But by the time Ted is closing his eyes and saying to himself, "Trash can, remember a trash can!" the process is complete and the characters are clearly able to pull causal loops out of the air at will. They've acquired a kind of superpower. They've transcended time travel.

*

Overall, Excellent Adventure, as well as being a cult hit, has consistently found praise for its elegant, totally internally consistent model of time travel. I believe this model is also unexpectedly deep, and that this internal consistency isn't something which came about by accident but because it was written by people who were paying attention, conscious that there is a sophistication to simplicity. There is a certain amount of skill in making a time travel story "sit right" with the viewer, in dodging or effortlessly pre-empting difficult questions, and certainly in word choice and phrasing. A time travel story can run an incredible distance on one good turn of phrase.

Also, there is essentially nothing you can do to avoid relentless analysis on the part of time travel geeks, and we are nearly impossible to please. By that measure, this may be the best time travel film ever made?

*

Except... they never actually closed those causal loops, did they? Never went back and stole the keys, never recorded the tape, never sent the fax, never rigged the trash can.

Not that it's out of character for the characters to forget about all that stuff, but the whole story is busted. Suspension of disbelief broken, zero stars.

Time travel in Bill & Ted's Bogus Journey

"I, too, can play the time game."

There's relatively little time travel in Bogus Journey, past and future history having been adequately explored in the first film. What time travel does appear doesn't contradict what we've already seen and theorised in the first film, which is why this is more of an appendix than a separate writeup.

At the outset of the film it seems that Bogus Journey might be going down exactly the same route as Terminator 2: Judgment Day - unexpectedly switching from a fixed history model to a malleable history model, flying in the face of all extant evidence. If De Nomolos' threat had appeared late in Excellent Adventure, it would have been difficult to take seriously, because we spent the whole film being shown over and over again that everything is rigid and internally consistent. It would be a radical change in the presented rules of the universe. But here, at the start of an entirely new film, the threat is far more credible, because so is the suggestion that the rules might not be what we think.

De Nomolos wants to go back in time to assassinate Bill and Ted when they were at their very weakest. He wants to change history, eradicating Bill and Ted's detestable music forever. Moreover, and much worse from our perspective as time travel analysts, he wants to raise the unhealthy question of what, exactly, happens when you try to alter history:

Rufus: "You won't get away with it."

De Nomolos: "Time will tell."

Rufus: "Time has told!"

De Nomolos: "I will go back and change that."

Of course, he fails, because he's wrong. Time is fixed, it cannot be altered. The good will win out, Wyld Stallyns' music will unite the whole universe. Rufus, naturally, is fully aware of the nature of history and causality, and tries to tell his former teacher so.

The real question then, is: What exactly does De Nomolos think he's trying to achieve? What does he think will happen if he alters history? Is his head filled with wrong ideas, or does he have no clue at all?

One of the things I like most about the Bill & Ted films is that they are loaded with extremely positive messages, many more than "Be excellent to each other" and "Party on". One of these, shown loudly and clearly in the first film and a little more stealthily here, is that study is important, and studying history is particularly important. Rufus himself, the most important figure in Bill and Ted's lifetimes, is revealed in this film to be a professional history teacher, at a respected higher learning establishment built in honour of Bill and Ted themselves. Meanwhile: De Nomolos' background? A gym teacher. His principal failing, the source of his villainy, is that he has no understanding of history, neither of its immutability or of his own deeply ironic role in it. By going back in time to broadcast Bill and Ted's deaths to the world, he inadvertently causes their climactic first show to be broadcast globally instead, kicking off the entire Bill and Ted utopian future. Yet another classic causal loop - a more pedestrian, accidental one, in this particular case.

*

A few more things come up towards the end of the film.

Firstly, there does indeed seem to be no anchoring phenomenon. Bill and Ted successfully execute sixteen months of intensive guitar training in a matter of objective seconds through the judicious use of time travel, never needing to jump a full sixteen months forward in time. (I mean, maybe it's a temporary thing and they do end up disappearing for sixteen months, later, but... this constraint isn't a prominent plot point in this film, so it's neither here nor there.)

Secondly, it briefly appears that the villain, too, can conjure causal loops at will. Honestly, this really caught me off-guard the first time I watched the film, instantly radically increasing De Nomolos' threat level. Could it be true, could De Nomolos have deliberately rigged the sandbag to take his gun out, and the cage to trap him, so as to give the appearance to Bill and Ted of falling into a causally looped trap of their design, then rigged himself a key and a second gun? Is De Nomolos' grasp of time travel physics better than I first thought?

Unfortunately, I'd forgotten the hard-earned lesson from earlier. De Nomolos cannot win, because we have seen a future in which he did not win. Bill and Ted win, and as Ted says, reaching the end of this actually really complex line of deductive reasoning impressively quickly, "Only the winners are gonna be able to go back and set things up!"

*

But they still never went back and followed through, did they? Car keys, tape recording, fax, garbage can, sandbag, cage, key and prop gun. Eight things which it looks increasingly unlikely that Bill and Ted will ever remember to take care of.

What's going on here? Will this most egregious omission ever be resolved? Will there really be a third film? Will it, as most people seem to be predicting, be entitled Bill & Ted's Unprecedented Expedition?

Alright, that's all I've got.