The goal of this blog post is to achieve the following:
- Introduce the concept of parsimony as used by scientists to those unfamiliar with the term.
- Examine how common rhetoric adopted by members of the left and right often lacks in parsimony.
- Explain why a lack of parsimonious reasoning dangers our society and our understanding of the truth.
The Law of Parsimony advocates choosing the simplest scientific explanation that fits the evidence.
The law of parsimony is foundational to all scientific disciplines and yet is surprisingly misunderstood by scientists and the lay public alike. Often equated with Occam’s Razor, the law is not a cry to always choose simple over complex explanations of natural phenomena. Instead, the law stresses choosing simpler explanations if that simpler explanation fits the entirety of the collected data. Thus if one finds that, while exploring the causal factors that generate phenomenon Z, causal factor A accounts for 30% of Z, causal factor B accounts for 50%, and causal factor C accounts for 20%, she should conclude that Z = A + B + C, and not worry herself over additional causal factors so long as the observed evidence is fully accounted for. Want a more concrete example? Suppose Martha is trying to understand why her pencil falls to the ground when she lets it go from her hand. After some basic research, she concludes that Newton’s laws of gravity can fully explain this phenomenon of interest. Martha’s friend Doug, however, suggests that while the laws of gravity are responsible for some of the pencil falling to the ground, there also exists millions of invisible leprechauns that catch falling objects and guide them towards the ground. Doug and Martha both provide explanations of the same natural phenomenon but Doug’s explanation adds unnecessary causal factors. What’s more, Doug’s explanation is also very difficult to falsify, even though there’s no evidence to support it. 100% of Z can be accounted for by A (gravity), thus adding B (invisible leprechauns) adds nothing to our understanding of why the pencil falls to the ground. Because it adds nothing, parsimony suggests we drop it from our equation.
If you don’t find my thought experiment compelling, take the evolution versus intelligent design debate. According to a 2017 Gallup study, 38% of Americans maintain a belief consistent with intelligent design such that, “human beings have developed over millions of years from less advanced forms of life, but God guided this process,” compared to 19% who believe a purely evolutionary account, “human beings have developed over millions of years from less advanced forms of life, but God had no part in this process,” and peculiarly unique to this country, 38% of Americans believe in a purely creationist view whereby, “God created human beings pretty much in their present form at one time within the last 10,000 years or so.” Let’s put the creationists aside and just look at believers of evolution versus believers of intelligent design. In trying to understand why human beings exist in their current form, both groups believe that “human beings have developed over millions of years from less advanced forms of life,” but defenders of intelligent design add an additional causal factor. This claim makes all the same predictions as the purely evolutionary model and does not explain any more of the available data. What’s more, the claim is not falsifiable, because it doesn’t make any unique hypotheses that we could then test. For these reasons, we drop this added causal claim and are left with a more parsimonious explanation about the existence of reality.
Lately, I worry that much of the rhetoric used by sects of the left and right relies too heavily on the construct of society as an unnecessary causal factor to explain behaviors they deem unacceptable. Society, by which I mean a collection of cultural factors, in my opinion, has become the ultimate straw man to explain the existence of “bad” behaviors. In doing so, we often talk past each other. If Martha and Doug live in a world where falling pencils is a big issue, it does no good if Martha suggests we use what we know about the laws of gravity to solve this issue, while Doug advocates for trying to understand more about invisible leprechauns. In the remainder of this post, I wish to briefly explore what I view as a lack of parsimonious reasoning by some members of the right on gun violence and by some members of the left on gender differences. Importantly, I do not wish to imply that societal pressures do not influence human behavior. Society clearly plays a role in shaping our behavior, though quantifying the extent to which societal pressures influence behavior is notoriously difficult. Additionally, I am not suggesting that just because some behavior is likely to be strongly influenced by biological forces that that excuses this behavior nor makes it an acceptable one nor does it make it a particularly useful behavior to exhibit. Surely my desire to consume sugary foods is rooted in biology, that I don’t eat a Twinkie every time I see one is, of course, a behavior that benefits both my society and myself. But as our political climate and general national conversation seems to increasingly struggle with the concept of truth, I offer a parsimonious reductio ad absurdum of recent political arguments in hopes that readers will apply similar logic to other important domains.
The Right on Gun Violence
Following the recent mass shooting in ________ (please fill in accordingly), the debate over what is to blame for the incredible amount of gun violence in this country continues to be a hot-button political issue. For many on the right, the issue of gun violence is not about guns but society. Everything from video games, political correctness, lack of religion taught in schools, and not being nice to potential school shooters has been offered as a causal explanation for why this country seems to exhibit such a disproportionally large number of gun-related deaths compared to other parts of the developed world. But unlike the invisible leprechauns, these claims can be easily falsified because they make testable predictions. The testable claim is that violence is caused by some combination of the previously mentioned societal factors. We know, however, that conspecific violence, especially among males, is as about as universal of a trait as they come. Societies around the world and throughout history have demonstrated horrid examples of violence and mass killings. Many of these societies did so without video games, or a culture of political correctness, or not teaching about God in their schools. Thus, these added causal factors are unnecessary to understanding what is really a rather simple natural phenomenon. Humans (like all animals) all around the world and throughout history show signs of violence towards each other. A society that allows nearly everyone to have access to guns (weapons that expedite the killing of other people) will likely result in significantly more gun-related violence and deaths than societies that don’t allow such.
While the exact percentage of gun violence (Z) that can be attributed to both A (natural human tendencies towards violence) and B (access to guns) is unclear, what is clear is that adding additional causal factors need only be necessary if there is evidence that new Factor C is actually causally related to gun violence. If gun violence is not affected by varying amounts of Factor C (let’s say political correctness on television), then Factor C is likely not an influential factor in explaining gun violence. Computationally, if Z = 87% = A + B + 2C in one society and in another society equally matched on A and B, Z = 87% = A + B + 4C, we conclude C = 0 and is thus not necessary to our understanding of gun violence. In this case, the right arguing about societal factors that they claim cause gun violence without evidence for such claims is a straw man that distracts from actual more productive conversations.
The Left on Gender Differences
In a very similar fashion, there are members of the left who have adopted a rhetoric and philosophy whereby all differences between men and women are said to be caused by societal and patriarchal forces. Again, societal influences on behavior are clearly evident, and varying cultural gender stereotypes have had profound and often negative impacts (particularly for women) on individuals throughout history. However, to suggest that all gender differences are the result of societal pressures both lacks parsimony and is also factually wrong. What’s more, it offers the potential to be a useless and unproductive narrative to espouse in many situations. Take for instance, a recent report of a 7% pay gap in male/female Uber drivers conducted by economists from Stanford University, the University of Chicago, and Uber. When the story first broke, many people were perhaps rightfully frustrated and angry. The patriarchy is at it again they claimed. However, looking at the data painted a much different picture of this story. The entire algorithm that pairs a driver with riders, dictates ride cost, pays drivers, etc. is completely gender blind. Thus there is nothing about the Uber platform that favors male over female drivers. What’s more, for the rides that were called and then canceled, no sex differences were found, thus it is not as if customers were canceling more once they learned their driver was female. So what did account for the difference? About 50% of the difference can be accounted for by the fact that men on average drive faster than women on average. The other 50% was accounted for by the locations that male and female drivers choose to drive in and their experience using the app. What should we make of these differences? Is the fact that men drive more quickly than women in more dangerous areas a product of the patriarchy or sexist advertisements or subliminal messages that we tell our young boys? More likely, this behavior can be explained by the fact that males of nearly all species are more likely to engage in risky behaviors in all facets of life. Additionally, we must ask how we would design an intervention to reduce this gap and more importantly, would it even be ethical or responsible to do so? Perhaps it’s a good thing, even a very good thing, that women are less willing sacrifice the lives of themselves and their passengers just to make $0.07 more on the hour. Why would we want to change what is objectively a very smart and rational behavioral decision? Again the left arguing about societal factors that they claim cause gender differences in this specific instance is simply wrong, and reflects poorly on the general validity of the feminist movement and the important issues the movement seeks to address.
Conclusion
Ultimately, what I hope to have achieved in this piece is not to mock, or offend, or shut out those who maintain the views that I view as lacking in parsimony. Rhetoric that does such is unlikely to bring about much change. As such, in this post I have specifically avoided advocating for any type of increased gun control legislation in this country and I have also not stated any denial of a legitimate gender-based pay gap that is in some way affected by gender discrimination. What I want readers to recognize is that when we assign something blame, we are inherently talking about causal relations (this caused that, thus this is to blame). What I am arguing, therefore, is that when speaking about gun violence or gender differences or any other topic, we should strive for parsimony in our reasoning. We should not add causal factors that add nothing to explain the phenomena, especially if the behavior can be fully explained in their absence.
When we start blaming society for everything, we take away the meaning of this causal factor. Additionally, when parties start making these highly un-parsimonious claims, they tarnish their image and the issues they care about and make others more skeptical of their claims. When Doug claims the pencil falls to the ground because of gravity and leprechauns, and continues to argue that his society focus on leprechaun based intervention strategies, he loses credibility. The same is true for when the right and left argue that society is responsible for much of gun violence and specific gender differences respectively. When the arguments of whole parties become so obviously flawed and inaccurate, allegations of fake news, conspiratorial motives, pandering, identity politics, etc. become all the more credible and perhaps even supported by available evidence. In a society that is seemingly struggling now more than ever with the concept of truth, we would do well to remember the law of parsimony in formulating our own claims, and evaluating those of others.
