Suppressed Evidence
David Kyle Johnson
Did you know that disco record sales were up 400% for the year ending 1976? If these trends continue... AAY!
Disco Stu, The Simpsons, “The Twisted World of Marge Simpson”
The fallacy of suppressed evidence is as simple as it seems: one commits the fallacy when one presents evidence or an argument for a position but leaves out (or suppresses) relevant evidence that would weaken or show false one’s conclusion.
In the quotation that opens this chapter, Disco Stu (a classic Simpsons character) is arguing that now is a good time to invest in Disco. Stu, however, leaves out a large portion of important evidence that would refute his hypothesis: years of slumping disco sales since 1976.Now, of course, it’s not always fallacious to suppress evidence. If some piece of information is irrelevant to your conclusion, you probably should leave it out. Or if it helps your case, but it would probably lead to an unwanted distracting discussion, it’s probably acceptable not to bring it up. But when you intentionally leave out evidence that would hurt your case, that’s suppressing the evidence. And this fallacy is important to understand because of how common it is and all the different forms it can take.
The name of this fallacy might make you think of when, in a courtroom, a lawyer for the prosecution suppresses evidence of the defendant’s innocence - and that is one example. But it is perhaps most common as a tactic in misleading advertising. In 2009, Olay suppressed the fact that, in ads for their wrinkle-eliminating eye cream, images of their spokesperson (the 62-year-old actress Twiggy) had been retouched. That same year, Kellogg’s suppressed the fact that the studies showing Frosted Mini-Wheats could boost attention in kids by 20% were highly dubious. The herbal supplement Airborne had to pay $23.3 million when it was shown that there was no evidence of its immune-boosting properties.
The list goes on and on: Sketchers Shape-Ups don’t tone your ass; Activia doesn’t make you poop; and Extenze doesn’t extend (Weinmann and Bhasin 2011).But, of course, scientific evidence is not the only kind of evidence that one can suppress. Sometimes the relevant evidence is simply context; without it, information or quotations can be highly misleading. Take quotation mining, for example. Modern Christian opponents of homosexuality often quote Leviticus 20:13, “If a man lies with a male as with a woman, both of them have committed an abomination.” But this verse lies in the middle of a huge list of Old Testament laws and commands, most of which modern Christians largely ignore - like those that forbid eating pork and shellfish (11:4-12), sex during a woman’s period (18:19), mixing fabrics (19:19), trimming one’s beard (19:27), getting a tattoo (19:28), and charging interest on loans to the poor (35:37). Of course, one might reply that since God’s prescribed punishment for homosexuality is more severe than the punishment for these others, we should still take this law seriously today (unlike the others). But notice that this reply also involves suppressing evidence. The prescribed punishment is death, yet few modern Christians suggest the death penalty for homosexuals. Touting the first half of a verse, while ignoring the second, is a textbook example of quotation mining.
But, of course, scripture is not the only thing that is quotation mined; so too are politicians. Take this quote from President Obama’s 2012 campaign: “If you’ve got a business - you didn’t build that. Somebody else made that happen.” His opponents repeated this, ad nauseum, as proof that Obama thought business owners deserved no credit for their accomplishments because they didn’t actually build their own business. But, in context, the quotation takes on a whole new meaning:
If you were successful, somebody along the line gave you some help. There was a great teacher somewhere in your life.
Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you’ve got a business - you didn’t build that. Somebody else made that happen. The Internet didn’t get invented on its own. Government research created the Internet so that all the companies could make money off the Internet. The point is, is that when we succeed, we succeed because of our individual initiative, but also because we do things together. (Blake 2012)In context, it’s quite clear Obama’s “that” - in “you didn’t build that” - referred to roads and bridges, not businesses. That is what business owners didn’t build.
Suppression of evidence is also commonly found in the (mis)presentation of statistics. For example, in 2012, when the Bush tax cuts were set to expire, a cable news outlet presented a graph which suggested that the result would entail a fivefold increase in the top tax rate. But the graph started at 34%. If it had started at 0, the increase wouldn’t have seemed so dramatic. Essentially, the (original) graph suppressed the evidence by suppressing the rest of the graph. In fact, it also suppressed some historical evidence as well. The highest marginal tax rate was around 90% after World War II; include that fact and letting the Bush tax cuts expire would seem inconsequential.
Scientific evidence can also be suppressed. Sometimes a scientific fact can seem to be good evidence for a claim when the “full story” reveals it’s obviously not. For example, as John Rennie points out, those who deny anthropomorphic climate change often point out that natural processes produce more CO2 than humans ever could; indeed, it’s true that 95% of the CO2 released into the atmosphere each year is from natural processes. Sounds convincing, right? How could humans possibly be responsible for global warming in light of this evidence?
What the deniers don’t realize (or fail to mention) is that natural processes also subtract CO2 from the atmosphere - so much so that their net effect is zero.
Humans, on the other hand, add tons of CO2 without taking it out - which means that, each year, we add far more than natural processes do. This is (one of the many reasons) why climate scientists think humans are responsible for levels of CO2 in the atmosphere rising to their highest point in millions of years (388 parts per million compared to the typical 284).Suppression of evidence is perhaps most common among conspiracy theorists. For example it’s true that, when shot, JFK’s head moved “back and to the left” - that is, toward the point that Oswald’s bullet would have entered Kennedy’s head, not away. (Oswald’s sniper point was behind Kennedy.) Does this mean there was a second shooter that shot Kennedy from the front right? Is that what made his head move back and to the left? No. Kennedy’s head moving back and to the left is actually what you would expect if Oswald was the lone shooter and shot Kennedy in the head from behind. Bullets don’t create a lot of resistance when they hit the surface of an object; they just pass though that surface. What creates motion is the explosion bullets cause. In Kennedy’s case, the front right of his head exploded - which pushed his head back and to the left. Don’t let what getting shot looks like on TV fool you.
The fallacy of suppressing the evidence can come from left, right, or center. According to The Skeptics Dictionary, scientists sometimes do it, reporters do it, and pretty much everybody does it now and again. And that
shouldn’t be too surprising; it’s an extremely effective (although underhanded) way to make one’s argument appear stronger than it is. But those interested in the truth should always present all the evidence they can, regardless of whether it hurts or hinders what they want to believe.
References
Blake, Aaron. 2012. “Obama’s ‘You Didn’t Build That’ Problem.” The Washington Post, July 18. https://www.washingtonpost.com/blogs/the-fix/post/obamas-you- didnt-build-that-problem/2012/07/18/gJQAJxyotW_blog.html (accessed October 4, 2017).
Weinmann, Karlee, and Kim Bhasin. 2011. “14 False Advertising Scandals That Cost Brands Millions.” Business Insider, September 16. http://www.businessinsider. com/false-advertising-scandals-2011-9?op=1 (accessed October 4, 2017).