Cross-posted from my blog.
[Editor's note: expect spoilers for the Elder Scrolls series generally, as well as Metal Gear Solid and Knights of the Old Republic.]
In The Elder Scrolls II: Daggerfall, timelines are strange. The initial conditions of the game are complicated, but fairly typical, when it comes down to it: there are a few different kingdoms in the Iliac Bay, all vying for power, and a kind of WOMD - Numidium - powered by a magical artifact, the Mantella. Using the Numidium, each of the individual kings is hoping to win ascendancy over his rivals in the Bay; the Emperor is hoping to unify the Bay and restore Imperial rule over the area; the Orcs are hoping to establish their own independent state; and some supernatural beings are hoping to achieve immense personal power through the Mantella. The player-character, although ostensibly backed by the Empire's spy network, can of course choose to pursue any of these goals. He or she will come into possession of the Mantella, and have to decide who deserves what end. Great! All those things we seem to love in games: multiple options, different consequences for our actions, and a good fight one way or the other.
Of course, the problem arises whenever you introduce multiple endings to a game - how do you negotiate the state of the world at the beginning of a sequel, if you want to produce one? The multiple outcomes of Daggerfall are quite robustly different: they involve the creation of a new kingdom, or of new gods, or the subjugation of people under an Imperial banner. The lives of millions are at stake. By the time TESIII:Morrowind rolls around, how do we expect people to discuss the Iliac Bay incident? The ES games have always relied heavily on in-lore writing: there's an acceptable degree of fallibility in characters' knowledge. People in Morrowind (the province, and the game) are sufficiently removed from those events, in time and in space, that they don't necessarily provide an accurate picture of what happened at the end of the last game. This kind of argument from ignorance is not an implausible way of explaining this phenomenon. Other games have used a similar system. In the original Metal Gear Solid, there are two possible endings. In one, Solid Snake's love interest, Meryl, is tortured to death, and Snake escapes with Otacon; the two remain fast friends in the rest of the series. In the other, Meryl survives, she escapes with Snake, and Otacon manages to extract himself of his own gumption. For a while, speculation remained as to whether Meryl had lived or died, and which ending was more appropriate to the series, and to Snake's character, but ultimately, Meryl showed up again in MGS4. The retcon was less a change of facts and more a change of interpretation; it was suggested that if the player had escaped with Otacon, Snake was simply mistaken - Meryl hadn't died, but was severely wounded, and was later found by government agents inspecting the site of the game's events.
A somewhat more nuanced (but perhaps less useful) approach was employed by the Knights of the Old Republic series, in which the player could (in true Star Wars fashion) either save the galaxy or set up shop as the new Sith Lord to destroy it. By the time the next game takes place, the main character was directly asked by an NPC if he or she remembered the events of the original. The player has clear dialogue options which will ultimately decide the truth of the matter: whether the player-character in the first game was male or female, and whether they sided with the Jedi or the Sith. In each successive playthrough, you could re-determine the issue, and explore the consequences of different actions.
To return to Daggerfall, however, what makes that game unique is that it does not take either approach. Instead of trying to negotiate five or six endings into one by virtue of information selection, or letting the player decide what happened on a meta-narrative plane, the solution is totally in-world, while simultaneously a tongue-in-cheek acknowledgement of the problem. When the magical Mantella is activated, it causes a Dragon Break, a magical event with the outcome that all the endings simultaneously and truly occur. The civil war ends in a relative stalemate, because every king wins and loses the war; the Orcs do create their own state, but are also defeated by the other kings; and the Empire re-establishes control over the area. There's a weird in-lore technical discussion of it over at the Imperial Library website which suggests what happens - namely, that when the timeline is skewed, the Dragon Break retroactively changes the past to fall in line with the new present conditions. Yes, it's confusing, and quite a few characters and books in the game devote time to speculating on what exactly happened, and how.
In a strange way, however, the game may have been looking forward to more recent developments in science - namely, quantum mechanics. There's a quality of particles known as quantum superposition which suggests how a particle can exist partially in multiple states of potentiality, due to the way probabilities overlap with each other. The double-slit experiment is the most common example of this process taking place. Scientists basically set up a reactive wall behind a shield with a single opening, and fired one electron through it at a time. So far so good. However, when they added a second opening to the shield, instead of seeing the electrons go through one opening or the other, they appeared to go through both openings simultaneously. More specifically, rather than going through both openings as particles, they seemed to act like waves, which (to put it bluntly) are quite different from particles. If you try to observe this happening, however, the waves coalesce back into particles. What's actually happening is relatively simple wave interference, like ripples on water where two stones have dropped, and the crest and troughs represents different possible outcomes. And this isn't only true of single particles like electrons - buckyballs do it too, and they're composed of sixty carbon atoms linked together in a soccer-ball-like crystal. If you're familiar with Schrödinger's Cat, that thought experiment is basically a way of asking the question, "What happens if we try to apply this quantum mechanical property to classical, normal-sized objects?" The results are weird. Dragon Break weird. In a sense, Daggerfall ends in a totally legitimate way - a huge scale-up state of superposition, in which every possible ending of the game does take place, no matter which one you personally observe as you finish playing the game.
On the meta-narrative level, this also happens in KOTOR. At the beginning of KOTOR2, your character from the last game might be any of four archetypes - male/female and good/evil - and they probabilistically overlap. The possibilities only coalesce into a real person when you decide, at the beginning of KOTOR2, that Revan was a man who fell to the Dark Side and regained his throne as a Sith Lord. But there's a meta-narrative conceit that takes place: we understand that although those three alternatives exist in the dialogue box, they exist because the game designer is allowing us to take command of the storyline in this particularly instance. He's winking at us and saying, "Go ahead, pick whatever option you went with from KOTOR." In TES, this isn't the case. Even the eponymous Elder Scrolls themselves are blind to the events of the Dragon Break. And as in the double-slit experiment, without an observer, the wave form will never coalesce. All possible states are superposed.
Can we find a way to make this happen in games? A way to model worlds in which unobserved events are superposed until an external factor forces them to coalesce into a single state? There's a problematic way we currently deal with side-quests: they're static, or they're static until we create conditions which make them impossible. (In The Witcher 2, for instance, side-quests are open for a whole episode, until you make one step past the point of no return and the game will suddenly alert you that you've failed five quests all at once!) What if, instead, the smaller conflicts and cycles of the game world waiting for you to arrive, they actually developed upon your arrival? Instead of finding the same set of side-quests waiting for you each time, you might that one side in a conflict had gained an advantage over the other - that the problem had been solved without you, or had become a different one entirely - or you might find that nothing was the matter in the first place. Maybe on its own, it doesn't seem like much, but the mentality of possibility could go a long way towards the next step in building rich game worlds which actually seem alive.