Fallacy of Exclusion and Suppressed Evidence

_{May 31 . 2004}

Important evidence which would undermine an inductive argument is excluded from consideration.

In an induction, the total relevant information needs to be examined. The fallacy occurs when relevant evidence which would undermine an inductive argument is excluded from consideration. The requirement that all relevant information be included is called the principle of total evidence.
Chhanda, Logic: Informal, Symbolic, and Inductive, p. 48.

Examples

On Deceptively Edited Video

“After dismissing election monitors, an official in Fulton County, Georgia continued counting in the dark of night. This is the ‘smoking gun’ proving election fraud in the 2020 US presidential election.” Following sworn affidavits and video evidence, Rudy Giuliani and Jacki Pick testified before the Georgia state legislature that the video shows fraud. However, the video was highly edited and failed to include extended footage of the ballots in question being brought in and boxed in the light of day.

Withholding exculpatory evidence in a murder trial

“Kyle Rittenhouse’s legal team accused prosecutors of holding back key video footage that is at the heart of their case in a formal motion for a mistrial, court documents show. … Prosecutors gave the defense a hard-to-see, low-res version in a 3.6MB file — less than a third of the high-res file they actually had, the motion states. They only got the better-quality clip, already used by prosecutors, on Saturday, after testimony had concluded, the motion stated.
“Prosecutors withheld high definition footage“, in The New York Post (November 17, 2021).

In the Kyle Rittenhouse case, video evidence was central to exonerating him. Withholding or degrading video evidence in a murder trial is paradigmatic example of suppression or exclusion.

A key piece of evidence was withheld in another murder trial, that of Noura Jackson.

The evidence was a handwritten note from a key witness at trial. His name is Andrew Hammack. He was the only person who testified that Noura was at the scene of the crime at the key period in which her mother was killed and a time when Noura was unaccounted for. … The Tennessee Supreme Court, when it reversed Noura’s conviction, found that the defense could have used this note to completely undermine Andrew Hammack’s testimony
“Guilt By Omission“, All Things Considered, NPR (August 4, 2017).

On partial plaudits on movie posters

Many movie ads, for example, include positive comments from critics, such as ‘One of the year’s best movies’ or ‘Hilariously funny — Gene Siskel gave it a thumbs-up.’ But when was the last time you saw an ad for a movie that mentioned that Roger Ebert gave it a thumbs down?
Carrick, The Persuasive Pen, p. 183.

A related example is the growing phenomenon of movie trailers excising just a positive word or phrase — “ingenious”, “mindbending” — even from reviews which were negative on the whole.

On citing selected studies

When someone makes an argument but leaves out a particular fact that would contradict the conclusion, they commit the Fallacy of Exclusion. This was committed on a grand scale by a 2004 Oxford study on the abortion-breast cancer link. Considered by many pro-abortion groups as the ‘end-all’ study on the matter, it consisted of a comprehensive review of over 50 studies on the possible link of abortion to breast cancer. While the conclusion was that no such link existed, the study’s lead author, Valarie Beral, admitted to the Washington Post that they excluded many studies that had found a link and contradicted their conclusion, citing only an unproven belief that women with breast cancer ‘are more likely then healthy women to reveal they had an abortion, leading to the conclusion that there are more abortions among this group.’ The failure to include data that compromised the desired conclusion is evidence of a Fallacy of Exclusion.
Nowak, Guerilla Apologetics for Life Issues, pp. 14-5.

On taxes and emphasizing parts instead of the whole

Take, for instance, the accounts widely circulated in 2000 about how the tax burden has shrunk to its lowest level in 40 years, with those earning under $30,000 (half of all taxpayers in the year 2000) paying a mere 2 percent of all income taxes. The strong implication of these stories was that the bottom half of taxpayers cannot complain, since they pay such a small amount of all taxes. Overlooked (on purpose? accidentally? out of ignorance?) was the fact that other kinds of taxes are a much greater burden to the bottom 50 percent of income earners than are income taxes. … [M]ost of these stories failed to note that when all taxes whatsoever are added up, the bottom half of the population pays a higher percentage of their income in taxes than do those in the very high-income groups.
Kahane & Cavender, Logic and Contemporary Rhetoric, pp. 62-3.

Conversely, “tax the rich” advocates will only ever offer tax rates instead of tax sums paid.

Warren Buffett has famously stated that he pays a lower tax rate than his secretary, but as this report documents this situation is not uncommon. This situation is the result of decades of the tax system being tilted in favor of high-income households at the expense of the middle class. Not only is this unfair, it can also be economically inefficient by providing opportunities for tax planning and distorting decisions. The President has proposed the Buffett Rule as a basic rule of tax fairness that should be met in tax reform.
The Obama Administration, “The Buffet Rule” (April 2012).

Let’s change the rigged tax code so The Person of the Year will actually pay taxes and stop freeloading off everyone else.
Senator Elizabeth Warren, via Twitter (December 13, 2021).

Buffet apparently paid $23.7 million in taxes from 2014-2018, exponentially more than his secretary, and “the rich” account for the vast majority of US taxes paid. Elon Musk paid more in taxes in 2021 than anyone has ever paid.

Frequently encountered is the situation where one piece of evidence is discounted because by using it, the result does not fit the forgone conclusion. … People … draw conclusions first, then select evidence that supports the conclusions and discount evidence that does not. A common example is the interpretation of land descriptions. People believe they already know what they own; therefore, regardless of the wording in the description, the conclusion must be what they meant when they wrote it, despite what they actually said. As the court stated in the case of Smart v. Huckins, “it is a matter of fitting the deed to the land, not the land to the deed.”
Wilson, Forensic Procedures for Boundary and Title Investigation (John Wiley & Sons: 2008), p. 50.

Critique

Give the missing evidence and show that it changes the outcome of the inductive argument. Note that it is not sufficient simply to show that not all of the evidence was included; it must be shown that the missing evidence will change the conclusion.

Anyway, the point of becoming familiar with the fallacy of suppressed evidence is to sharpen one’s ability to spot cases in which relevant evidence is being passed over, whether by others or by ourselves. We need, in particular, to learn how to carry through reasoning so as to see whether all likely relevant information has been considered.
Kahane & Cavender, Logic and Contemporary Rhetoric, p. 62.

Commentary

On overlooking evidence because of an ideological bias…

Of course, people who suppress evidence often do so inadvertently, one reason that a more all-encompassing label for the fallacy might be overlooked evidence, or perhaps slighted evidence. It’s easy, when strongly committed to a particular side of an issue, to pass over arguments and reasons on the other side. In recent years, advocates on both sides of issues such as capital punishment, abortion, the legalization of marijuana, the depiction of violence on TV, and the legalization of prostitution, frequently have been guilty of slighting evidence damning to their side of the issue. Those opposed to “three strikes you’re out” legislation, for instance, tend to neglect the ways in which this kind of law might protect society from repeat offenders; those in favor don’t like to talk about the high costs associated with keeping people in jail long past the age at which the vast majority of criminals have ceased to commit violent crimes, or about the fact that a great many of those sentenced under these laws have not committed violent or even serious crimes. ¶ We all, of course, sometimes are motivated by more crass considerations than mere overzealousness. Self-interest is a powerful motivator of deliberately shady reasoning, as is self-deception.
Kahane & Cavender, Logic and Contemporary Rhetoric, p. 62.

On sharing all the data from an experiment

For example, if you’re doing an experiment, you should report everything that you think might make it invalid – not only what you think is right about it: other causes that could possibly explain your results; and things you thought of that you’ve eliminated by some other experiment, and how they worked — to make sure the other fellow can tell they have been eliminated. … The idea is to try to give all the information to help others to judge the value of your contribution; not just the information that leads to judgment in one particular direction or another.
Richard Feynman, “Adapted Caltech 1974 Commencement Address“

On intentional and unintentional suppression…

Fallacies of suppressed evidence may be committed either intentionally or unintentionally. If the author of the argument intentionally omits known relevant information, the fallacy is deliberate deception. The omission of relevant evidence which the author knows may, however, be a simple blunder; the author may simply have forgotten to consider some of the available relevant facts. It may also happen that an author has included among the premises all the relevant information he or she knows, but that others know relevant information of which the author is unaware. Here again, the argument commits a fallacy of suppressed evidence, but again the fallacy is unintentional. The author has done his or her best with the available information. … Suppressed evidence should not be confused with implicit premises. Implicit premises are assumptions that the author of an argument intends the audience to take for granted. Suppressed evidence, by contrast, is information that the author has deliberately concealed or unintentionally omitted. Implicit assumptions are part of the author’s argument. Suppressed evidence is not.
Nolt, Rohatyn, & Varzi, Schaum’s Outline of Theory and Problems of Logic, p. 36.

On the ideal of total evidence…

Some logicians argue that the requirement of total evidence is too stringent, that no argument can incorporate all the known evidence to a given conclusion. With respect to arguments involving very complex issues, this may well be true. For such arguments, the requirement of total evidence is a theoretical ideal, seldom (or perhaps never) attained in practice. Consequently, inductive arguments on very complex issues will generally suffer to some degree from the fallacy of suppressed evidence. the best arguments will be those who minimize suppressed evidence and suppress no evidence that drastically affects the probability of the conclusion. In many simple cases, however, the requirement of total evidence is quite stringently met.
Nolt, Rohatyn, & Varzi, Schaum’s Outline of Theory and Problems of Logic, p. 37.

On whether it is a logical fallacy, strictly speaking…

For example, Hurley cites a case in which a used car salesman sells a car to a woman, but fails to tell her that the odometer had rolled around twice and that the engine had two cracked pistons and a burned valve. Hurley claims that the salesman’s argument in this case commits the fallacy of suppressed evidence, where an argument presents evidence for a conclusion but ignores stronger evidence that supports a different conclusion. In this case, we can say that the salesman lied about the engine and, therefore, that he has acted unethically. … But has he committed a logical fallacy, in particular, the fallacy of suppressed evidence? ¶ This type of criticism, pointing out that a fallacy has been committed, imposes a requirement on the salesman’s argument that it must ‘tell the whole truth,’ so to speak. His argument must not omit relevant evidence. He has an obligation in the context of the dialogue to present all the relevant evidence, or enough of it so that no stronger evidence supporting any other conclusion is left out. This is actually quite a high standard for an argument to meet in order to be nonfallacious. Leaving out relevant evidence could be an indicator of bias, or it certainly is a good indication that the argument is weak and incomplete. But is the defect a serious enough one in context that we are justified in saying that the salesman has committed a logical fallacy?
Walton, The New Dialectic, p. 230.

On Misusing the Ellipsis…

An ellipsis is an omission of words, usually indicated by a series of periods. We use ellipses all the time as a matter of convenience or emphasis — to shorten text or oral statements when space or time is limited, drawing a reader or listener’s attention to what is relevant to the discussion at hand. When used properly, an ellipsis brings focus or brevity without sacrificing meaning. But, like a kitchen knife, it can be twisted in service to a darker purpose. In his satirical classic, Devil’s Dictionary, a work that maliciously mocks hypocrisy and the misuse of language, American author and journalist Ambrose Bierce defined “quotation” as “[t]he act of repeating erroneously the words of another.” Bierce perhaps had the misused ellipsis in mind; in the hands of a rogue, the ellipsis can turn a speaker’s original meaning on its head. Simply take a quotation, neatly trim away the words that don’t support your argument while leaving in place those that do, and you have embarrassed your opponent and misled your audience. Sadly, the ellipsis, misused, can leave lasting effects; studies from psychology tell us that false statements are notoriously persistent and difficult to counter. Fortunately the misused ellipsis is easy to reveal; one need only consult the original material to reveal the truth.
Levin, “Misusing the Ellipsis” at Mediation Channel, Sep. 11, 2009.