Works of fiction, including episodes of The Twilight Zone, are, or appear to be, representations of possible worlds. Insofar as they succeed in representing what is possible, they do represent possible worlds. In their simplest form, a work of fiction represents a single possible world that differs from the actual world. The differences usually involve individuals who don’t exist in the actual world, but are posited as existing in the possible world represented. The work of fiction can also include objects that don’t exist in the actual world, and events that haven’t occurred in the actual world. In several episodes of The Twilight Zone, including “The Parallel,” more than one possible world is represented, and this raises a special metaphysical problem, namely: Can there be a story “about” two possible worlds, or are we stuck with two stories, which can’t be brought together?
The first possible world described in “The Parallel” is the world of early 1960s astronaut Robert Gaines, who is set to take off on a rocket and orbit the earth. Robert Gaines is a fictional character, of course, who undergoes events similar to events in the actual world. In 1964, in the actual world, NASA had begun a successful series of manned spacecraft flights, including flights that involved a spacecraft orbiting the earth before returning to earth in a “splashdown.” These early flights were by no means routine. They each involved using new technology for the first time, and revealed new information about space flight and the effect of spaceflight on human cargo. “The Parallel” borrows much of the scientific and historical context from the actual world, and contributes a set of fictional characters who negotiate this world that is very similar to ours.
The episode trades on the limits of our understanding of space travel, particularly at the time. In flight, communication is lost between the astronaut Gaines, and mission control on the ground. Suddenly and inexplicably, Gaines is back on earth, in a military hospital, with no idea of what transpired since losing contact.
What we, and Gaines, very slowly come to appreciate, is that Gaines has left what is represented as the actual world, and is now an occupant of a different possible world, one very similar to the actual world he was in when he left the ground, but clearly different in what might seem like minor respects, but different nonetheless. In his “home” world, his home did not have a picket fence. But in the world he now occupies, it has a picket fence. In his home world, he drank coffee with sugar. In his new world, he does not take sugar in his coffee. In his home world, John F. Kennedy is president of the United States. In his new world, it is someone else. More significantly, when Gaines and his wife kiss, we can tell that she realizes immediately that she is kissing someone other than the Robert Gaines to whom she is married. The daughter also detects that something is off. She exclaims, “Daddy, you’re different!” As she later clarifies, what she means is that it isn’t daddy at all, but someone else.
So our story now has two stories: There’s the possible world in which Robert Gaines takes off in a spacecraft and loses contact with mission control. In that world, JFK is president. Let’s call that world “world-1.” There’s a possible world in which Robert Gaines lands a space ship also after experiencing a blackout. In that world, JFK is not president. Let’s call that world “world-2.” In world-2, Gaines is identified by others as Robert Gaines, though his wife and daughter soon have their doubts. In world-2 Robert Gaines identifies his co-workers and his family as the individuals he’s known before the flight.
The two stories are connected by containing the same individual, Robert Gaines, who is represented as existing in both worlds. Robert Gaines travels from world-1 to world-2. No one else travels across worlds. The person who he takes to be his wife in world-2 is not his wife. She’s back in world-1. And he is not the husband of the world-2 wife. We don’t know where her husband is, our Robert Gaines’s counterpart, but her husband, wherever he is, is not our Robert Gaines, i.e. someone who is an astronaut while JFK is president.
Can these two possible worlds be unified in this way? Of course there are incongruities, and many of these are discovered by Robert Gaines, and he is alarmed by them. Yet they are explained away as his confusions, perhaps as temporary mental illness as the result of his outer space travel. In world-2, everyone else is in agreement about who is president, for example. If he is right about who is president, then everyone else is wrong. The temptation to attribute mental illness to Gaines indicates that there is a problem of coherence, but the incoherence is at a higher level.
It is true of Robert Gaines in world-1 that JFK is his president at time t. If Gaines were to travel to another possible world, as the episode suggests, one in which JFK is not president at time t, then it would be both true of Gaines that JFK is his president at time t, and false that JFK is his president at time t. Since this is a contradiction, and so not possible, it is not possible for Gaines to travel from world-1 to world-2. One way of putting it is that there can be no trans-world identity. The same individual cannot be part of two different possible worlds (See Lewis, 1986, pp. 210 ff.). Another is that there can’t be overlap. Two possible worlds can’t share the same members.
The metaphysics of possible worlds and counterparts is also the subject of “Mirror Image.” In the discussion of that episode we raised the very issues that are front and center in “The Parallel.” The main difference is that “Mirror Image” depicts an individual and her counterpart occupying, at least temporarily, the same possible world, while in “The Parallel” we see Gaines “invading” a possible world, which, if our reasoning above is correct, he can’t possibly invade.
Lewis, David, (1986) On the Plurality of Worlds, Basil Blackwell.