What determined the respective fates of the twins? Were their futures foretold by Rebecca’s oracle, or rather, by its interpretation? Were their fates traded through the exchange of a bowl of lentil stew for the birthright? Or was it Isaac’s blessing, secured through subterfuge, that sealed the respective paths of the boys? Was it all of these things together, or perhaps none of them, that determined that Esau would become a ruffian, while Jacob would emerge as the spiritual father of a people covenanted to God?

Twins are a source of fascination, especially for scientists who research the relative influence of genetics and environment in human development. But even non-scientists wonder about siblings who gestated and were born together, were raised in the same environment, and yet whose paths diverged dramatically one from the other. Twins provide a special vantage point into the nature/nurture dichotomy, and allow us to imagine that it is possible to resolve the mystery of character if we can just isolate the inputs of genes or environment.

Such efforts to simplify human development are, however, prone to fail. True, there are physical characteristics and even some personality traits that are heritable, and there are certainly environmental influences that affect character development. And yet, it is never simple to say that entirely because of parentage, or parenting, that a person became the way that they are.

I suspect that the Torah provides three explanations for the divergent paths of Esau and Jacob in order to undermine the sense of certainty that many people have about why things happened the way the did. Maybe it was this, or maybe it was that, or maybe something else entirely. Take the oracle that Rebecca hears. It seems clear enough, ורב יעבד צעיר, but this phrase could mean either, “the older shall serve the younger” or, “the older–shall be served by the younger.” (the musical notation on the first word, tiphah, is a disjunctive, which would favor the second reading). If Rebecca knew what was sure to happen, why did she try to affect the outcome? Was she backing up the divine plan, or undermining it? Maybe there wasn’t a plan at all, just a hint of a possible future.

The truth is that it is seldom one factor that sets the course of life, but rather, a series of decisions, some well thought out and others stumbled upon, that direct and then redirect our lives. It is easier to think that the big things are out of our control. Indeed, on some level, at some point, we all believe in predetermination—that things happen for a reason—and that individual agency is an illusion. Determinism comes in many guises, as the historian Niall Ferguson writes in his book, Virtual History, which uses counterfactuals to deepen understanding of the many possible futures at any given moment of history. There is, of course, theological determinism, the idea that God sets the course of history (predestination), and also intervenes (providence), and that free will is therefore an illusion. In the Talmud, Rabbi Hanina says, “all is in the hands of heaven, except for fear of heaven” (Ber. 33b, Meg. 25a, Niddah 16b). Rabbi Akiva describes this as a paradox—“All is foreseen, but choice is given.” That is, go ahead, and make your choice, but God already knows what will happen.

Many modern thinkers, perhaps influenced by  Newton’s bold laws of motion, developed  theories of history that were largely deterministic. From Montesquieu to Adam Smith, and from to Hegel to Marx, it became common to minimize the role of individual agency and instead assert the overwhelming power of impersonal forces that shape society. For some reason, people like to think that things—even terrible things—are just bound to happen, and thus there is little point fretting about what went wrong. The point is to notice what’s coming and to prepare yourself, rather than think that you can change history.

While Judaism, as I have said, certainly has a strong current of deterministic thinking, it is also adamant about the significance of choices. Tempting as it may be to accept our fate, Judaism teaches us to cast a critical eye on our environment, to determine what needs to change, and then to plan intense and extended action until we can reshape our environment. Western cultures have also reacted to the theories of historical determinism, sometimes veering to the opposite extreme of “the great man view of history” that was common in the mid-20th century. We need more nuance—awareness of the broad economic and cultural forces that influence events, but also confidence that determined individuals can form alliances and change the narrative and the outcome of a group.

Let’s look at one crucial moment of the portion, at Genesis 27:30. “As Isaac completed blessing Jacob, and Jacob was just leaving the presence of his father Isaac, then Esau his brother came in from his hunt.” This verse is very dense with names—five of them, and with active verbs. I detect a pun in the Hebrew—akh yatzo yatza Yaakov—the first word, which I have translated as “just” sounds like the word for brother—Jacob has just left his brother’s guise, when in came his brother Esau.   אל תקרא אך יצא אלא אח

In any event, the key thing is that these characters all believe that their actions matter. Isaac thinks that his blessing has determinative power, and he trembles in dread upon discovering that is has been misdirected. Given the risks involved, Jacob must be sure that his receipt of the blessing (whether stolen, or rightfully claimed) will be efficacious. And Esau certainly feels, upon discovering what has transpired, that he has been robbed of his future.

What is truly frightening in this entire episode is the willingness of each member of the family to do violence to the others in order to get his or her own way. Rebecca and Jacob are quick to take advantage of Isaac’s blindness; Esau threatens to murder Jacob, and even Isaac seems unable to recognize that he has caused his family dynamic to devolve into chaos. A certain amount of sibling rivalry was predictable, and indeed predicted, but the extreme acrimony experienced in this family by the end of the portion is their own doing. Twenty years later, in a moment of great tension, Jacob and Esau will meet again, and finally they will end their strife. They will not spend the rest of their lives at war after all, and neither must their descendants.

For nearly two millennia Christians and Jews were locked into mutually exclusive covenantal narratives. Our people suffered grievous persecutions as a result. But in recent decades we have found our way to a new relationship more akin to that of loving siblings. The friendship between Rabbi Avraham Skorka and Pope Francis, discussed this week at JTS, is certainly an example of the change that is possible. Perhaps in another century the current enmity between Arabs and Israelis, which seems inevitable and predetermined, will be displaced, as two distinct peoples learn to live peacefully together. If so, it will not happen automatically, but because people of vision and courage worked tirelessly to change the relationship.

We should not assume that hatred and violence are predetermined. But neither may we expect that resolutions of bitter controversies will occur automatically. It is our responsibility to seize opportunities to change the narrative, so that brothers who fought from the womb will eventually stand together, embracing with tears and kisses.