Fact Checking and Logic Checking



As mentioned in this introduction to logic checking, the LogicCheck project was modeled on the work of an established fact-checking community, including principles of transparency, accountability and non-partisanship. The commitment to transparency and accountability are described in this statement of principles, and I hope the articles you have read over the last three months give you confidence that examples of good and poor arguments will continue to be selected without favor to any party or position.


Given how popular fact-checking has become over the last several years, it’s reasonable to ask what the logic-checking approach I’m explaining and advocating for adds to that already established and important practice.


I’d like to illustrate what fact-check producers and consumers could gain from supplementing what they do with an example from recent events: House Speaker Nancy Pelosi’s tearing up President Trump’s speech at the end of his most recent State of the Union address.


Calling the Speaker’s act bold or childish is a matter of subjective opinion. But there were two claims made about Pelosi’s action that can be evaluated more concretely: (1) that it was illegal; and (2) that it was pre-meditated.


Claims that Pelosi broke the law by tearing up an official government document were first floated in conservative media circles, and later taken up by President Trump himself. Two prominent fact-checking organizations: Politifact and FactCheck.org, did what fact-checkers do best: professional journalism (including interviews with experts and research of statutes and case law) to demonstrate that Pelosi’s act – whatever you think of it – did not represent illegal destruction of government property.


Given what you now know about the logic-checking process, you might have already discerned that Pelosi’s accusers were actually making this simple valid, but unsound argument:


Premise 1: Nancy Pelosi tore up a copy of the State of the Union speech President Trump handed her.

Premise 2: That copy of the speech was official government property, destruction of which is an illegal act.


Conclusion: Nancy Pelosi broke the law by tearing up the President’s speech.


The argument is valid, in that accepting all of the premises as true requires you to accept the conclusion as true. But it is unsound since, as those fact-checkers pointed out, Premise 2 is false (or at least easy for a reasonable person to doubt).


Because this argument hinges entirely on the truth or falsehood of the second premise (given that the first premise is obviously true), declaring the conclusion to be false because that premise is false is reasonable shorthand for the more complete logic-checking process you just read. But what happens when the situation being analyzed is not so clear cut?


Enter the accusation that Pelosi’s tear was pre-meditated, meaning that she had planned to rip up the President’s speech on national television before she had any idea what was in it. If that accusation is true, it would mean her act was more of a publicity stunt than a sincere act of outrage over what the President had to say during the State of the Union.


Like many situations, this accusation claims to know what was going on in someone else’s mind, a notoriously difficult thing to prove definitively. In theory, a confession by Pelosi could establish this claim, as could iron-clad evidence, such as a dumpster full of torn documents she practiced on days before the speech.


Given that the House Speaker has denied accusations of pre-meditation, the Principle of Charity requires we seek other ways to prove otherwise, rather than just dismiss her as a liar. While we don’t have that aforementioned dumper of evidence, one web journalist did post a highly trafficked tweet which claimed to show Pelosi had prepared the document for ripping at the start of the speech, a claim taken up by media organizations.


As with the “Pelosi broke the law” example, we are dealing again with an argument, one that reads:


Premise 1: Nancy Pelosi claims she ripped up President Trump’s speech because she was outraged by what she read in that speech.

Premise 2: Video evidence shows Pelosi preparing to rip the document at the start of his speech, before she heard or read the speech in its entirety.

Conclusion: Nancy Pelosi planned to rip up President Trump’s speech in advance.


Here we have not a deductive argument, but an inductive one, in which the conclusion must be judged based on how likely it derives from the premises. In this case, if all the premises are true it is still possible to reject the conclusion, even though every premise being true makes the conclusion very likely to be true as well (making this a strong argument).


However, it turns out that the crucial second premise isn’ttrue. As Politifact pointed out, video and images of slightly torn pages came from near the end of Trump’s speech, rather than the beginning. This is an example of how a bad premise might not ruin an inductive argument, but can significantly weaken it since “priming” pages a few minutes before tearing them in half supports Pelosi’s claim to have been motivated to act spontaneously (or nearly spontaneously) out of outrage over the speech itself.


Claiming that this revised evidence proves the conclusion is false would itself be a false statement since we are still not in a position to prove truth or falsehood of the accusation definitively. But we can say definitively that the argument supporting the accusation, especially given the revised timeline for the second premise, is very weak.


Note that my claim that the argument is very weak is NOT a matter of opinion, but rather a matter of fact, just as real as any objective fact that can be checked for truth and falsehood. But by taking the logic-checking approach, I can say something definitive about a statement that cannot be proven or disproven through fact-checking (really premise-checking) alone.


The reason I did not title this piece Fact Checking vs. Logic Checking is because it turns out – as demonstrated with my first example – fact checking is actually a special kind of logic-checking, a shorthand version which can be deployed when arguments hinge entirely on the truth or falsehood of a premise.


But many of the most important things we discuss and debate hinge on more than just factual information. The claim that global warming is false because we’ve had three cold winters in New England doesn’t fail because the facts are wrong (presuming we have had three cold winters) but because they do not provide sufficient reasons to accept the conclusion. In other words, it is a failure of logic versus a failure of fact.

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