Some years ago a cousin told me he had discovered an old steamer trunk belonging to my father in the attic of the farmhouse where my dad had grown up and where my aunt had continued to live until she was past 100. (By this time my father had been dead for more than a decade.) When I got a chance to investigate, I found the trunk contained some old clothes, a U.S. Army overcoat and armloads of books, papers, photographs and memorabilia belonging to a young man whose early life had been largely unknown to me.
I found a packet of letters in the trunk that my father had written home during his time as a Harvard graduate student in Argentina in the early 1940s and later as an army draftee during World War II. The woman who would become his wife and my mother, a fellow graduate student studying in Argentina, was mentioned in a couple of letters home, but only in passing. Then I came across three letters in my mother’s handwriting addressed to my father in Buenos Aires. In the first, dated January 29, 1943, she announced that she had left town for a few days and asked him not to be angry or hurt. In the next, dated February 7, she begged his forgiveness for “the unintended melodrama” and told him “I was never designed for a femme fatale.” If I didn’t know better, I might have concluded my mother was trying to write a “Dear John” letter but couldn’t quite bring herself to do it. However, in her third letter to my father, undated but apparently written some time after the first two, she referred to herself as his fiancé. In the final paragraph she scolded him, “You’re terribly impatient because you’re in love, and because you haven’t much time.” Indeed, he did not. There was a war on, and my father received a notice from his draft board, dated March 3, 1943, ordering him to return home “at the earliest possible date for a physical examination preparatory to being inducted into the service.” In a few short months my father would be going through basic training in Spartanburg, South Carolina.
Did my father win the girl and live happily ever after? There were no more letters in the trunk. But, of course, the story didn’t end there. I am proof of that. Yet I couldn’t help wondering what might have happened if the balance had tipped ever so slightly in the other direction, and my mother had broken things off before my father heard from his draft board. Life presumably would have gone on more or less as before, oblivious of two little people whose problems didn’t amount to a hill of beans in this crazy world. There was a war on, after all. My mother and father would have gone their separate ways. My father’s streamer trunk would presumably still have gathered dust in my aunt’s attic, and the contents would have been the same – minus that third letter in which my mother referred to herself as my father’s fiancé. But, of course, for me and for my siblings, for our children and grandchildren, the omission of that third letter could not have been more consequential. You wouldn’t even have been able to point to the tragedy of lives not lived, since we never existed at all.
An untimely “Dear John” letter from my mother was by no means the only threat to my existence before I even existed. My father fought in World War II, earning three battle stars. He was part of the Normandy invasion, although not on D-Day itself. His closest brush with death – at last so far as I know – came far from the front line on a park bench in London in 1944. He had been reading the Sunday paper, got up and walked away just before an incoming German V-2 rocket turned the park into a crater.
We can all point to events in our lives where an outcome could have gone one way or another, with momentous consequences for all concerned. It doesn’t have to be something that would turn the tide of history, like Robert E. Lee winning the Battle of Gettysburg or Lee Harvey Oswald missing his target when he pulled the trigger in Dallas. There is a whole body of popular literature called alternate histories to entertain us with such possibilities. For most of us, however, the events that separate what happens from what might have happened are small -- so small that we might not even recognize them as events until after the fact: a letter sent or not sent, a Sunday paper read or lingered over on a park bench in London.
Our ability to imagine what might have been is lodged in the prefrontal lobes of the brain, along with such higher cognitive functions as symbolic speech, abstract reasoning and foresight. Neuroscientists call it “counterfactual thinking,” meaning that we are able to contemplate things that are not immediately present in our sensory experience. This is what enables us to ask “why” and to run through “what if” scenarios. There are obvious evolutionary advantages in being able to anticipate future outcomes and to make adjustments. It is less clear what advantage there is, apart from pure entertainment value -- in being able to consider what might have happened if Hitler had won World War II or the Russians had beaten us to the moon.
At one time, leading scientists argued that there are no possible alternatives to what actually happens, because everything is determined by inviolate natural laws. According to the physicist and mathematician Pierre Simon de Laplace (1749-1827), if you knew the position, direction and velocity of every particle in the universe, you could determine their state at any other time, past or future, using the laws of classical physics alone. Every action, including our thoughts and intentions, would be precisely determined from the beginning of time until its end. According to this hypothesis, sometimes referred to as “Laplace’s Demon,” I needn’t have troubled myself with the thought that my mother might have walked out on my father before I was even a gleam in their eye. Nor was there any chance a V2 rocket might have landed on my father while he was reading the Sunday paper on a park bench in London.
Laplace’s Demon was called that because it would take a “demon” of infinite intellectual capacity to know the position, direction and velocity of every particle in the universe in order to determine their past and future states. But, as it turns out, there is an even bigger obstacle to any practical application of Laplace’s thought experiment. Quantum physicists in the early 20th century determined that elementary particles don’t behave according to the laws of classical physics; specifically, they don’t have a fixed position and velocity that can be determined, at least not at the same time, which means that future conditions are a matter of probabilities rather than precise determination.
Once we are in the realm of probabilities, anything presumably might happen. Furthermore, since quantum rules now apply, every possible outcome of an event might play out in a parallel universe somewhere (not to be confused with alternate histories as a popular literary genre). This is the so-called “many worlds” interpretation of quantum physics, which follows Yogi Berra’s dictum that when you come to a fork in the road, you should take it. There is never a path not taken in the quantum realm, at least according to Stephen Hawking and other leading physicists. In my mother’s case, she could have sent my father a “Dear John” letter or not; both options would play out in parallel universes. Similarly, my father might have not have survived his near miss with the V2 rocket in some other universe. But in this one he lived to tell the tale -- and consequently so did I.
It occurs to me that there may be a parallel universe somewhere in which the “many worlds” interpretation itself doesn’t exist. The idea of many worlds was first put forward in a 1957 doctoral dissertation by an American physicist named Hugh Everett. But what if a near-facsimile of Everett’s mother in a parallel universe wrote his father a “Dear John” letter before they married, and the two went their separate ways. Hugh Everett would never have been born, and his “many worlds” hypothesis would not have been proposed. That universe would otherwise be very much like this one, right down to nearly identical versions of me in each one. How could you tell the two worlds apart? To begin with, this essay would only exist in one of them.