“No Time Like the Past” is another of many episodes addressing the possibility of time travel and the philosophical issues raised by it.
The episode begins with an argument about the risks associated with time traveling to the past. Paul Driscoll argues that there are risks associated with existing in the present, such as the risks of nuclear war and environmental pollution. He argues that such risks either didn’t exist in the past, or were significantly less than the present. In terms of minimizing such risks, traveling to the past is preferable than staying put.
It’s true that time travel to a past (or future) with more favorable environmental conditions would lower the health risks associated with new exposure to such hazards, but it wouldn’t eliminate the effects of exposure from the period prior to time traveling. Further, traveling to the past means traveling to a time when medical treatment for environmental exposure of the sort Driscoll describes is either far less advanced, or non-existent. Driscoll seems to overlook these and other risks unique to the time traveler.
Although his motivation seems to be the desire to escape from the undesirable features of the age into which he was born, Driscoll chooses to “visit” three moments in the past that have great historical significance: the nuclear bombing of Hiroshima in 1945, Hitler’s rise to power in the Berlin of 1939, and the sinking of the Lusitania in 1915. In each case, Driscoll attempts to alter the course of history. In Berlin, for example, he rents a room with a clear shot at Hitler. He prepares his long gun with a scope, and takes aim. But he is interrupted, and the chance to kill Hitler is missed.
These three scenarios illustrate what Lewis calls a paradox of time travel. On the one hand, when Driscoll is in Berlin and has all the conditions set for killing Hitler, it certainly seems possible for him to do so. Even when he fails to take aim and shoot, we would like to say that had he not been interrupted by the house staff of the hotel, he would have been able to shoot Hitler.
While shooting Hitler would be possible if Driscoll were a normal inhabitant of 1943, he is not, and we have to take that into account when considering what it is possible for him, as a time traveler from the future, to do. Suppose Driscoll could kill Hitler in 1943. Then it would be true in 1964 that Hitler was killed by a sniper, Driscoll, in 1943. But it would also be true that Hitler was not killed by a sniper in 1943, and that he consolidated power in Germany and was largely responsible for World War II. Since this contradiction follows from the assumption that killing Hitler in the way Driscoll does, by time traveling to 1943, the assumption has to be rejected.
Driscoll’s attempted interference in the sinking of the Lusitania also illustrates the incoherence of changing the past. Just before the torpedo is directed to the Lusitania, Driscoll tries to convince the captain to make a one degree change in the direction of the ship. But Driscoll can’t provide any reasons that are acceptable to the captain. Even the weak suggestion that nothing would be lost by making such a small correction is not convincing. Why take an action when there is no reason to do so?
After these three forays to the past fail to bring about the desired changes, Driscoll lowers his sights, and claims that he just wishes to travel to an earlier time when life was less taxing and less dangerous. He plans to live merely as a spectator, rather than as an actor. He chooses Homeville Indiana in July of 1881 as his destination in space and time. The question now is this: Can one retire to the past the way one can retire to a country retreat?
One difficulty Driscoll faces in Homeville is that political events and political opinions are all around him. He realizes that he has arrived just as U.S. president James A. Garfield is about to be shot. The knowledge of the inevitability of the outcome of this assassination attempt weighs heavily on him. Though he doesn’t attempt to prevent it, he somehow feels responsible for letting it happen, even when he now knows that it’s logically impossible for him to influence the outcome.
When Driscoll realizes that children will perish in a school fire in Homeville, he attempts desperately to prevent it, and in doing so appears to cause it. This is confusing, given the conclusion we (and Driscoll) have reached earlier, namely that it is impossible for a time traveler to influence the past. If Driscoll causes the fire, then Driscoll, an adult male in 1964 is the cause of a fire that occurred more than 100 years before his birth, and so this requires backward causation, where the effect occurs before the cause. It would follow from this that before Driscoll time travels to Homeville, no fire has occurred. But then it also requires that the fire has occurred, since if Driscoll caused it, the fire did take place in 1811. Again, there is no coherent description of Driscoll causing anything to happen while he time-travels.
So how do we read this scene in Homeville? One reading is to say that it reveals an incoherence in the story, and even worse, a blatant contradiction, where the author both explicitly claims that changing the past is possible and that it is not possible. A more charitable reading is that Driscoll only appears to cause the fire. Perhaps he thinks he did, and perhaps we are seeing the event from his perspective. Since that perspective can’t be what actually happened, what we witness is Driscoll’s mistaken view of what happened. If Driscoll could remind himself that he cannot bring about changes to events in the past, he could take comfort in knowing that he was not the cause of the terrible school fire.
Many puzzles about time travel and causation remain. Driscoll and Abigail fall in love. If this is right, then clearly his presence has caused changes in her emotions, beliefs, hopes and dreams. More mundanely, every conversation Driscoll has in Homeville involves some causal interaction with others. If this engaged participation in the life of the past can’t occur, it’s not clear how one could visit the past. Perhaps one could only visit it while being causally inert, outside some sort of causal bubble, looking in.
David Lewis, “The Paradoxes of Time Travel” American Philosophical Quarterly, Vol. 13, No. 2 (April 1976) pp. 145-152. (also suggested for “The Odyssey of Flight 33”)