Suppressed Evidence

98 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. Other examples concern the evidence offered for Skechers Shape‐Ups, Activia, and ExtenZe. The issue is whether the advertised benefits were supported, rather than whether every possible benefit was disproved (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 nauseam, 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; that comparison gives historical context, although it does not by itself show that the proposed change was 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 anthropogenic 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?

The missing context is that natural processes also remove CO2 from the atmosphere. Large exchanges in both directions can be roughly balanced, while an additional human source changes that balance. Natural sinks absorb some of the added carbon, but the remainder accumulates. The relevant quantity is the net addition, rather than gross emissions alone. The historical figures cited in this account describe atmospheric CO2 rising to 388 parts per million compared with a baseline of 284.

Suppression of evidence is perhaps most common among conspiracy theorists. For example, arguments about JFK’s assassination often emphasize that his head moved “back and to the left” after the shot. That observation alone does not establish a second shooter or a bullet’s direction. Such an inference requires the wider forensic evidence and an account of the forces involved, rather than an intuition drawn from how shootings look on television.

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, whether it supports or challenges what they want to believe.