Derek Turner writes . . .
In 2015, the following meme flashed across social media:
Folks on the political left shared this in large numbers, and with considerable righteous indignation. People complained that in all their years of schooling in the United States, no one had ever shown them this map! Why weren't kids taught about the Native American polities that were diminished or erased by Euro-American colonization and settlement? But then someone pointed out that this map was never intended to represent any actual historical political landscape. Oops. From the very beginning, it was an exercise in counterfactual history. What political units would exist in 2015, had the epidemics, the violence, and the displacement not occurred?
Those who didn’t already have egg on their faces quickly responded that even as an exercise in counterfactual history, the map is both far-fetched and ethically problematic. It’s ethically problematic because it still represents the erasure of many Native nations and communities that exist today. It also builds in an assumption that indigenous polities would develop into units that look like European nation states. And don't call the Puebloans of the southwest the "Anasazi." Here, though, I want to focus more on the epistemological than on the ethical problems. What the map represents seems far-fetched and speculative. I’m very confident in saying that. But what exactly are the grounds for making such an assessment?
A Multidimensional Epistemology for Historical Counterfactuals
In general, historical counterfactuals take the following form:
If some upstream condition A had been different, then downstream outcome C would have happened instead of what actually happened.
In an earlier post, I tried to make a little headway by drawing a distinction between preventing and enabling conditions. Some counterfactual claims are about upstream conditions that prevent downstream outcomes from happening, while other counterfactuals are about upstream conditions that make it possible for downstream outcomes to occur.
Here I carry the analysis further by distinguishing four other dimensions along which historical counterfactuals can vary. I’ll call these upstream departure, downstream departure, historical depth and historical slack.
Variation along these dimensions can affect whether counterfactuals are reasonable or (like the one above) far-fetched. My view is that it really is possible to assess counterfactuals, even when it comes to the deep past. There is, however, no easy formula for doing so. The assessment is always holistic and often messy. But identifying these dimensions of variation is a good start.
When thinking counterfactually, we can imagine bigger or smaller deviations from what actually happened upstream. To assess the degree of upstream departure, focus on the upstream conditions alone. It’s hard to be precise about the size of the upstream deviation from the actual, but some easy examples will make it clear that in practice, we often have a pretty good idea of what counts as a bigger vs. smaller upstream departure.
(1) If Senator Bernie Sanders of Vermont had won the Democratic nomination in 2016, then Donald Trump would not be president of the United States.
(2) If Senator Chris Murphy of Connecticut had won the Democratic nomination in 2016, then Donald Trump would not be president of the United States.
I don't know whether either of these statements is true, though I’m sure a lot of people believe (1). Note, however, that (2) involves a bigger upstream departure than (1). In making this judgment, we have to draw on background knowledge—for example, that Sanders and Clinton were engaged in a competitive primary race, and that Chris Murphy was not seeking the nomination at all. There’s a sense in which the departure described in (1) could easily have happened, whereas it’s very hard to see how the departure described in (2) could have happened. Claim (2) is also, I think, a lot harder to assess than (1), for the simple reason that we have less evidence about what sort of campaign Chris Murphy might have run, or how people might have responded to him.
Historical counterfactual thinking also involves imaginative departures from what actually happens downstream, and these, too, can be bigger or smaller. Thus:
(3) If Bernie Sanders had won the Democratic nomination in 2016, then he would have won the states of Michigan, Pennsylvania, and Wisconsin, defeating Donald Trump by a narrow electoral margin.
(4) if Bernie Sanders had won the Democratic nomination in 2016, then he would have won the general election in an electoral college landslide.
I'm not sure if claim (3) is true, but these sorts of claims are worth thinking about, if only because lots of people believe them. And people argue about them all the time.
Again, in order to assess the degree of departure from what actually happened, we have to consult our background knowledge. The results of popular voting in Michigan, Pennsylvania, and Wisconsin were pretty close, so (3) would seem to involve a small departure from the actual past. But popular voting results in many states, including a number of reliably red states, would have had to come out very differently in order for Sanders to win an electoral landslide. In this case, hopefully, it’s easy to see that (4) involves a bigger downstream departure than (3).
Historical Depth and Historical Slack
Historical depth is a matter of the amount of time that has elapsed between the upstream and the downstream conditions. The political examples above are all historically shallow, which also makes them a bit easier to think about. The counterfactual map of Native American political bodies is historically deeper. The counterfactuals we might care about in paleontology—like some of the claims that Gould makes in Wonderful Life—are vastly deeper.
Historical Slack has to do with the relationship between the upstream change and the downstream change. Here’s the rough idea: Historical counterfactuals are tight when the upstream departures from actual and the downstream departures move in tandem. That is, a tight counterfactual asserts that a big upstream change makes for a big downstream change. Or that a small upstream change makes for a correspondingly small downstream change. Historical counterfactuals exhibit more slack when the upstream departures and the downstream departures have different magnitudes—for example, where a small upstream change is said to lead to a big downstream change, or where a big upstream change is alleged to make little difference downstream. (Note: I'm treating slack as a feature of the counterfactual claims, rather than a feature of history itself.)
Rolling Back History
What I’ve said so far is really just an opening sketch. Much more needs to be said about how these four features—upstream departure, downstream departure, depth, and slack—bear on the question of whether it’s rational to believe counterfactual claims. And then much more needs to be said about how this might apply to questions about evolutionary history.
However, with nothing more than these opening distinctions on the table, it’s possible to glimpse an epistemology of historical counterfactuals that’s different from one standard approach. In his book, The Philosophy of Philosophy, Timothy Williamson describes an imaginative “rolling back” method for assessing historical counterfactuals—a method that sounds very similar to Gould’s thought experiment of replaying the tape of history, the topic of John Beatty's recent post, though Williamson seems unaware of Gould.
The offline use of expectation-forming capacities to judge counterfactuals corresponds to the widespread picture of the semantic evaluation of those conditionals as “rolling back” history to shortly before the time of the antecedent and then rolling history forward again according to patterns of development as close as possible to the normal ones to test the truth of the consequent.
So we rewind the tape of history in the imagination, make the upstream changes, and run the tape forward while holding as much fixed as we can.
[O]ne supposes the antecedent and develops the supposition, adding further judgments within the supposition by reasoning, offline predictive mechanisms, and other offline judgments … To a first approximation: one asserts the counterfactual conditional if and only if the development eventually leads one to add the consequent.
Apply this to the case with which we began: Roll back time, say, to 1492. Then “suppose the antecedent”—suppose that Europeans do not come to North America to colonize, settle, displace, or dispossess. Then roll history forward again, while relying upon other background knowledge. Do things end up as represented in the map above?
This account of the rolling back method is fine as far as it goes, but it doesn’t take us very far, because it doesn’t say anything about the differences among counterfactual claims, and how those differences might matter epistemically. What we need to do is contrast different historical counterfactuals, while focusing on the dimensions outlined here.
So What’s (Epistemically) Wrong With the Map?
One problem with the map, as an exercise in counterfactual history, is the magnitude of the upstream departure. The map exhibits considerable historical depth (500+ years), and a fair degree of tightness, since the suggestion is that huge upstream departures would have made for correspondingly big downstream changes in political outcomes. But the upstream departure puts out of play so much of what we know about the world, that it becomes very difficult to get a fix on what the resulting downstream departure should be.
But we should be careful not to conclude that bigger upstream departures always make for less plausible historical counterfactuals. Or that smaller upstream departures generally make for greater plausibility. Consider:
(5) If time-traveling Homer Simpson had sneezed 66 million years ago, then everyone today would have forked tongues.
(6) If no asteroid had hit the earth 66 million years ago, then humans would not exist today.
Whether someone sneezes is a much smaller change than whether an asteroid hits. Yet the counterfactual (6) with the much bigger upstream departure is vastly more plausible than (5). These examples, show, I think, that the assessment of historical counterfactuals has to be holistic and multidimensional. It won't work to focus on upstream departure alone. Much also depends, for example, on relevant background knowledge about the causal connections that might link the upstream with the downstream departures.
I shared some of these ideas with an audience at UCLA’s Cotsen Institute for Archaeology in November 2015. (This partly explains my use of a non-paleontological example here!) I also want to give a special thanks to Ramzi Kaiss for many helpful conversations about contingency and counterfactuals last year.
 But see Avi Tucker, Our Knowledge of the Past. Cambridge University Press, 2004, who tries to account for assessment of historical counterfactuals within a Bayesian framework.
 S.J. Gould, Wonderful Life: The Burgess Shale and the Nature of History. W.W. Norton, 1989.
Tucker says that that “when historiographic counterfactual hypotheses are overstretched across many causal links, evidence is missing for determining them” (2004, p. 231). This notion of stretching across many causal links is ambiguous between historical depth and historical slack.
 Timothy Williamson, The Philosophy of Philosophy. Blackwell Publishing, 2007, p. 150.
 Williamson (2007, p. 153.)