Logical Fallacies
including a short discussion of
inductive vs. deductive reasoning*
* ’cause that’s interesting...or it’s not. Either way.
Logical Fallacies
or
“How to Recognize When Someone Is Lying To You and Avoid unintentionally Doing It Yourself”
A Logical Fallacy
Let’s break this concept down…
Logic: Using rational thought, evidence, and reasoning to come to a conclusion (instead basing it on guesswork and emotions alone).
Logical: the condition of using logic
Fallacy: put simply, a mistake.
First, a word about types of reasoning:
In logic, we often refer to the two broad methods of reasoning as deductive and inductive. These are both good approaches to reasoning out a question we have, or proving a point, but they must be used in the right way and on the right occasion. In other words, both don’t work for all situations.
Deductive reasoning works from the more general to the more specific. Sometimes this is informally called a "top-down" approach. We might begin with forming a theory about our topic of interest. We then narrow that down into more specific hypotheses that we can test. We narrow down even further when we collect observations to address the hypotheses.
This ultimately leads us to be able to test the hypotheses with specific data -- a confirmation (or not) of our original theory.
Inductive reasoning works the other way, moving from specific observations to broader generalizations and theories. Informally, we sometimes call this a "bottom up" approach (please note that it's "bottom up" and not "bottoms up" which is the kind of thing a bartender says to customers when he's trying to close for the night!).
In inductive reasoning, we start with specific observations and measures, begin to detect patterns and regularities, formulate some tentative hypotheses that we can explore and finally, based on those, develop some general conclusions or theories.
Inductive reasoning: more open-ended and exploratory, especially at the beginning of the process.
I think [this] is true so I’ll look for evidence in my environment that proves (or disproves) it.
Deductive reasoning: more narrow in nature and is concerned with testing or confirming hypotheses.
I notice this and this, which leads me to think that [this] is true.
previous slides retrieved from: http://www.socialresearchmethods.net/kb/dedind.php
Do We Get It?
Which of these is inductive reasoning?
Do We Get It?
Which of these is deductive reasoning?
Logical Fallacies
What’s the best definition of a logical fallacy?
And now...
Some of the most common (and easy to miss)
Slippery Slope: This is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,..., X, Y, Z will happen, too, basically equating A and Z. So, if we don't want Z to occur, We must not allow A to occur either.
Example:
If we ban Hummers because they are bad for the environment eventually the government will ban all cars, so we should not ban Hummers.
In this example, the author is equating banning Hummers with banning all cars, which is not the same thing.
Hasty Generalization: This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts.
Example:
Even though it's only the first day, I can tell this is going to be a boring math class.
In this example, the author bases his evaluation of the entire course on only the first day, which is notoriously boring and full of housekeeping tasks for most courses. To make a fair and reasonable evaluation the author must attend not one but several classes, and possibly even examine the textbook, talk to the professor, or talk to others who have previously finished the course in order to have sufficient evidence to base a conclusion.
Is the example a Slippery Slope or a Hasty Generalization?
If I don’t go to the movie tonight, my social reputation will end up ruined!
Slippery Hasty
Slope Generalization
Is the example a Slippery Slope or a Hasty Generalization?
We left the concert halfway into the first song because the band was horrible!
Slippery Hasty
Slope Generalization
And now, since everyone loves a little Latin...
Post hoc ergo propter hoc: This is a Latin phrase that means “the last cause was of the first cause”. This fallacy assumes that if 'A' occurred after 'B' then 'B' must have caused 'A.'
Example:
I drank bottled water and now I am sick, so the water must have made me sick.
In this example, the author assumes that if one event chronologically follows another the first event must have caused the second. But the illness could have been caused by the burrito the night before, a flu bug that had been working on the body for days, or a chemical spill across campus. There is no reason, without more evidence, to assume the water caused the person to be sick.
Ad hominem: This is an attack on the character of a person rather than his or her opinions or arguments.
Example:
Green Peace's strategies aren't effective because they are all dirty, lazy hippies.
In this example, the author doesn't even name particular strategies Green Peace has suggested, much less evaluate those strategies on their merits. Instead, the author attacks the characters of the individuals in the group.
Is the example below a post hoc ergo propter hoc or an ad hominem fallacy?
Because I took a trip on an airplane, I got sick. Therefore, the airplane ride made me sick.
post hoc ergo ad
propter hoc hominem
Is the example below a post hoc ergo propter hoc or an ad hominem fallacy?
The immigration policy is wrong because the politician who suggested it is a lazy, mean lady who can’t even spell the word “economy”.
post hoc ergo ad
propter hoc hominem
Genetic Fallacy: This conclusion is based on an argument that the origins of a person, idea, institute, or theory determine its character, nature, or worth. This fallacy is often used by hate groups to marginalize, exclude, or target a set of people sharing specific traits. (Yuck!)
Example:
The Volkswagen Beetle is an evil car because it was originally designed by Hitler's army.
In this example the author is equating the character of a car with the character of the people who built the car. However, the two are not inherently related.
Begging the Claim: (Also called “loading the language” The conclusion that the writer should prove is conveniently validated within the claim by the word choice they use.
Example:
Filthy and polluting coal should be banned.
Arguing that coal pollutes the earth and thus should be banned would be logical. But the very conclusion that should be proved, that coal causes enough pollution to warrant banning its use, is already assumed in the claim by referring to it as "filthy and polluting."
Is the example below a genetic fallacy or a begging the claim fallacy?
The short-sighted, racist immigration policy is wrong, and should be abolished.
genetic begging the
fallacy claim
Is the example below a genetic fallacy or a begging the claim fallacy?
All the European settlers were elitist and spoiled. None of them cared about equality with the Native Americans.
genetic begging the
fallacy claim
Circular Argument: This restates the argument rather than actually proving it.
Example:
The speaker is a good communicator because he speaks effectively.
In this example, the conclusion that the speaker is a "good communicator" and the evidence used to prove it -- "he speaks effectively" -- are basically the same idea, said differently. Specific evidence such as maybe his effective use of language, how he breaks down complex problems, or how he illustrates his points with humorous stories would be needed to prove the claim.
Either/or: This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices.
Example:
We can either stop using cars or we will simply destroy the earth!
In this example, the two choices are presented as the only options, yet the author ignores the range of possible choices in between such as developing cleaner technology, using car-sharing systems for emergencies, or trying better community planning to discourage so much driving.
Is the example below a circular argument or the either/or fallacy?
All the European settlers were elitist because they thought they were better than everyone else.
circular either / or
argument fallacy
Is the example below a circular argument or the either/or fallacy?
If we don’t wear face coverings during the pandemic, we’re all going to die.
circular either / or
argument fallacy
Red Herring: This is a diversionary* tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them.
*diversionary: meant to distract then confuse an audience
Example:
The level of mercury in seafood may be unsafe, but what will fishers do to support their families?
In this example, the author switches the discussion away from the safety of the food and talks instead about an economic issue, the livelihood of those catching fish. While one issue may affect the other it does not mean we should ignore possible safety issues because of possible economic consequences to a few individuals.
Straw Man: This move oversimplifies an opponent's viewpoint and then attacks that hollow argument.
Example: People who don't support the proposed state minimum wage increase hate the poor.
In this example, the author attributes the worst possible motive to an opponent's position. In reality, however, the opposition probably has more complex and sympathetic arguments to support their point. By not addressing those arguments, the author is not treating the opposition with respect or refuting their position.
Is the example below a red herring or the straw man fallacy?
Forget about the hurricane off the coast of Galveston, what about the racial inequality in that city? Let’s talk about THAT!
red straw man
herring fallacy
Is the example below a red herring or the straw man fallacy?
If you don’t adopt a puppy today, you must not care about animals!
red straw man
herring fallacy
Moral Equivalence*: This fallacy compares minor misdeeds** with major atrocities.
* Equivalence: asserting that one thing is equal to another.
**misdeeds: doing something that is wrong or inappropriate in a certain situation.
Example: That parking attendant who gave me a ticket is as bad as Hitler.
In this example, the author is comparing the relatively harmless actions of a person doing their job with the horrific actions of Hitler. This comparison is unfair and inaccurate.
Bandwagon: This fallacy argues that a person should do a certain thing or believe a certain way because everyone else is. The implication, of course, it that since everyone else is doing it, that makes it right, or sound.
Example:
These [insert super-sweet popular brand name here] jeans are worn by millions who are happy, friendly, and very well-liked.
Get on the bandwagon, man!
Everyone’s buying ‘em!
In this example, the author suggests that if you buy/wear this particular brand of jeans, your life will improve. (As if!)
Is the example below a moral equivalence fallacy or the bandwagon fallacy?
Everyone is going to adopt a puppy. Don’t you want to get in on that?
moral bandwagon
equivalence fallacy
Is the example below a moral equivalence fallacy or the bandwagon fallacy?
The person who won’t adopt a puppy today, you’re as bad as an animal abuser!
moral bandwagon
equivalence fallacy
Logical Fallacies
Which two logical of the logical fallacies discussed in this slideshow do you most often see in media, be it online, TV, radio, etc? Provide an example along with each one.
Logical Fallacies
or,
“How to Recognize When Someone Is Lying To You, and Avoid [Accidentally] Doing It Yourself”