“The world is awash with bullshit,” Carl Bergstrom and Jevin West write. What is it? How do we recognize it? How do we call it out when we see it? Calling Bullshit: The Art of Skepticism in a Data-Driven World, informs us on these questions.

I first heard about this book following Bergstrom on Twitter. Like many, I started following him during the early days of COVID-19, when Twitter surfaced some of his informative, evenhanded tweets to me. Bergstrom was “calling bullshit” on media coverage and bad science about the pandemic, and so when I saw a tweet promoting this book, I became immediately interested.

The false objectivity of numbers

Perhaps my favorite part about this book was about how it pointed out the myriad ways in which numbers can be used to mislead. Bullshit is frequently hidden among seemingly-objective numbers, Bergstrom and West write:

Numbers are ideal vehicles for promulgating bullshit. They are objective, but are easily manipulated to tell whatever story one desires. Words are clear constructs of human minds, but numbers? Numbers seem to come directly from Nature herself.

This quote, 78 pages in, stuck with me for the entire book. The authors present example after example of how numbers can be used to mislead—intentionally or not—through presenting numbers without context, estimating from biased samples, or creating irrelevant comparisons.

Numbers, stripped of their context, are meaningless. At best, they can be unintentionally useless, but at worst purposefully misleading.

I’ve had a draft of a post titled “data nihilism” sitting for a while. I never got around to fleshing it out, but I wrote it when I was frustrated by how often COVID-19 “facts” were being stripped of their context. Seemingly objective numbers, like the positivity rate, number of deaths, or reproductive transmission rate, were all meaningless when devoid of context for what is ‘normal’ or comparisons to other regions or populations.

That’s how I felt reading Calling Bullshit. Seeing such a thorough treatment of the different, and simple!, ways that numbers can be used to mislead was refreshing. (And a little alarming!)

Spotting bullshit

One of the last chapters of the book is on how to spot bullshit effectively:

  1. Question the source of the information
  2. Beware of unfair comparisons
  3. If it seems too good (or bad) to be true, it probably is
  4. Think in orders of magnitude
  5. Avoid confirmation bias
  6. Consider multiple hypotheses

The authors walked through numerous examples of how these strategies could debunk bullshit:

  • that Roseanne being canceled caused Disney stock to drop 2.5% (no, one show didn’t cause that, and the drop happened before the news broke)
  • that there are 121,000 men in the UK named John Smith (off by an order of magnitude or more)
  • that international student applciations were down by 40% (no, they were down at 40% of universities, and up at another 35%)
  • that St. Louis and Detroit are the most dangerous cities by violent crimes per capita (it’s because their city limits are small)

The scientist in me was quite pleased by the tutorial on Fermi estimation, too. It’s one of the most useful skills I developed in school, and I find myself using it all the time to question numbers that I see in the wild.

Perhaps most importantly, this chapter, like the rest of the book, was incredibly accessible to the untrained reader. Nothing that Bergstrom and West wrote requires formal education or mathematical sophistication to understand. Above all, they teach critical thinking, and in particular critical thinking in a data-driven context.

Refuting bullshit

In the last chapter, we see how we might refute bullshit. “Find counterexamples” and “provide analogies” are among the plethora of strategies listed here, and I learned a lot from reading through them.

But the way the book closed truly surprised me—

Before you go out there and start calling bullshit willy-nilly, we would like to conclude with a few thoughts about how to do so in an ethical and constructive manner.

(Emphasis mine.) Be correct and clear, of course, but also be charitable in your assumptions about the other person (they’re probably not malicious! just misinformed), and admit fault when you make mistakes.

And perhaps most importantly, don’t be a “well-actually guy," they write. “A well-actually guy has more in common with a bullshitter than he does with a caller of bullshit.” (Yes! They spend two pages on why this practice is awful.)

This isn’t a book about how to be smarter than everyone else—it’s about how to make sense of the messy world we live in. “The world is awash with bullshit,” Bergstrom and West write. This book helps us to navigate it a little bit better.