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In Defense of Logical Fallacies


Logical fallacies are reasoning based on false logic. False logic weakens an argument. A logical fallacy can cause people to draw false conclusions. Those who use false logic can appear foolish to those who are well versed in logic. Using logical fallacies would probably hurt a student’s grade on a composition or term paper. The only excuse for using logical fallacies is they work.

This article will show how false logic works to get a desired outcome. It’ll also demonstrate why statements with logical fallacies shouldn’t be dismissed out of hand. In bringing up examples this article isn’t intending to make political points.

Petitio Principii

The circular argument is where a proposition is used for proof. My logic teacher admitting using this one to get her way. An example: She wanted her boyfriend to buy her a coat. To any argument he gave against such a purchase she would retort; “I want a coat”. Eventually he relented and bought her a coat.

The circular argument is a good way to get someone to give up on an unwanted discussion. The discussion is like yelling at an automated message. Authority figures use this argument all the time. “The law must be obeyed because it’s the law.”

Ad Hominem

This is an attack on the messenger rather than the message’s validity. Example: “Wine is good for you.” “You smoke.” The messenger smoking has nothing to do with wine’s health benefits.

“Where did you read wine is good for you?” “An article posted in a winery.” Pointing out the winery has a vested interest in displaying an article claiming wine has health benefits is a valid argument.

In the 1970s the U.S. Air Force instructions about “Rumors and Propaganda” advised its personnel when they hear something to “consider the source”. A friend or foe is not likely to share information that would make people less likely to behave a certain way. The friend or foe’s knowledge is irrelevant.

The smoker may have beliefs about a healthy lifestyle contrary to accepted medical guidelines.

Argumentum Ad Vercundiam

This is using a source of information that is no authority on the subject. One commentator wrote the sarcastic statement, “I know more about this subject than you because I read an article written by some idiot.”

Such appeals work for a variety of reasons. Over 100 scientists say this is or isn’t true. Few people would take the time to investigate how many of these scientists are in fields relevant to the what is under discussion? If someone says “none”, or “only a few”, few will confirm if that’s true. Appeals to actual authority can be deceptive. Some experts have good track records for being right, others have a knack for getting things wrong. As the warning about stocks go, past performance is not a guarantee of future performance.

Argumentum Ad Populum

This is claiming something is right because many people believe it to be right. Advertising agencies often use this technique: “The best-selling car in the country”, “the country’s favorite beer”, “the most popular new show on television”.

Logically the above statements, if true, should have no bearing on which car you should buy, beer you should drink, or television show you will watch. Why does this car sell so well? Is it the best car for the money? Is it the best car most people can afford? Does it have an attribute that many car buyers find appealing? These are three good reasons for purchasing this automobile. Why is the beer so popular? Does its taste separate it from the other beers? It makes sense to give a new hit television show a try. It's something you can discuss with family and friends.

Either-Or Fallacy

This is an argument where if one of a limited set of options is correct and the others are wrong. “You are either with us or against us” and “this is wrong so that is right.” There are often grey areas so a “zero” or “one” decision is not always appropriate. Computers work on the binary principle that an electrical current can either go in one direction or the opposite direction.

“Are you with us?” if “no” then “will help opposition by action or inaction.” “Will help opposition by action or inaction” equals “against us”.

Law is often written in an either/or manner. Have you exceeded the posted speed limit? Have you filed your taxes? Do you have knowledge of the whereabouts of a fugitive? The wrong answer to these and many other questions could mean fines and or imprisonment.

Secudum quid

Making hasty generalizations such as “someone who cheats at cards will also cheat at business.” Dishonesty in one area doesn’t indicate dishonesty is all areas. Should an employer overlook a job candidate’s cheating at cards and golf when making a hiring decision?

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What constitutes a “hasty generalization” is subjective. When does avoiding a hasty generalization become ignoring the obvious? Decisions often can’t wait for sufficient information to become available.

A standard product test involves subjecting test animals to far more of the product, relative to its size, than any human can possibly consume. The animals are tested for abnormalities. Tests are done this way because it is logistically impossible to have enough test and control animals for a study with realistic amounts of the product.


Faulty Causality is assuming because two events happen together or in sequence, then one event caused the other. I bowled a high score when I wore a red scarf, therefore the red scarf got me the high score. Logically the red scarf has nothing to do with bowling performance. It is possible believing the scarf gives an advantage could give a bowler more confidence and earn them a better bowling score. Logically, the only apparel that could affect a bowling score are shoes. Advertisers often claim athletic shoes will improve athletic performance. How much of the bowler’s improved performance is because of the shoe design and how much is psychosomatic? That is usually an open question.

There are times where one event causes another even though it’s unknown how the two events are related. A civilization doesn’t have to know about gravity to realize tides coincide with the Moon’s phases. Phenomena is usually observed long before there is a theory explaining why the phenomena happens. A bee flaps its wings and it flies. For many years the science said a bee couldn’t fly by flapping its wings.

Slippery Slope

This is the assertion that a step in one direction will lead to more steps in that direction and end badly. You are eating a potato chip. You will eat more and more and become morbidly obese. The fallacy is you can stop at just one potato chip. The reality may depend on the person. Some people can have a “just one” break in a diet, or one alcoholic drink a day, or skip a day of exercise. For other people the “just one” exception is the beginning of the end of what they are trying to avoid or accomplish.

Law is another matter. In common law a ruling makes a precedent. A sympathetic judge can expand that precedent. Those with an agenda can “shop” for a sympathetic judge. A court ruling can be used as a justification for subsequent actions. In the United States the Supreme Court’s 1905 ruling in the Jacobson v. Massachusetts has been used as a legal justification for imposing vaccine mandates during the COVID-19 pandemic.[i]

Debate to add or change laws are normally the status quo vs. moving in one direction. When a side gets a law passed that breaks the status quo how do they react? Does the side say; “we worked out an excellent compromise, we thank the opposition for preventing us from going too far”? Does the side say; “this law is a step in the right direction”?

[i] Liberty Champion, Vaccine Mandates: Court Precedents Support State Mandated Vaccines - The Liberty Champion, last accessed 3/17/22.

Strawman Argument

This is where someone presents opposing arguments just to knock them down. Punching holes into an opposing argument does nothing to prove your argument. Claiming flaws in an argument without someone to defend the argument is like fighting with a strawman.

When making a presentation about a new system it’s reasonable to address the misgivings and misconceptions people have about the new system. Attendees can consider it an evasion if the presenter doesn’t address these well-known arguments against the new system. Opponents of a proposed law frequently brings up reasons for not passing the law. It would be wise for proponents to explain why the reasons are invalid. Proponents of an action repeat facts that support the action. It’s reasonable for opponents to bring up facts that invalidate the proponents’ facts. Not countering the other side’s arguments gives the other side an open opportunity to say almost anything to support their side and knock down your side’s arguments.

Argumentum Ad Antiquitam

This is where the reason for doing something is because this has always been done. What makes this logic fallacious is what has been done previously could be superfluous, inefficient, or wrong. It’s possible the traditional approach is right.

In 1969 an expedition organized by Thor Heyerdahl, the Ra expedition, set out to prove it was possible to cross the Atlantic Ocean in a papyrus boat. They attempted to build a papyrus boat similar to the ones built in Africa in ancient times. These boats had papyrus bent over the boat. This gave them a scorpion like appearance. They looked cool and the expedition members assumed it was only for aesthetics. Reproducing the appearance proved difficult so they elected not to have this feature, since this pretty form had nothing to do with its function. The expedition failed. They concluded the scorpion like construction was for the hull integrity. In 1970 the Ra II expedition successfully crossed the ocean in a papyrus boat that had a scorpion like tail.[i]

It’s possible the ancient papyrus boat builders didn’t make the scorpion like tails for hull integrity. The hull integrity could have just been a byproduct. Flying wings weren’t originally designed with radar evasion in mind. The radar evasion capability was discovered during flight tests. By accident or design the traditional way might have an unknown benefit. It’s logical but not a good idea to simply dismiss tradition.

[i] The Ra Expeditions, TVI, Interwest Film © 1971.

Absence of Evidence

Logically, absence of proof is not proof of absence. Taking a course of action based on a supposition that has no evidence is a good way to waste resources. Pointing out absence of proof is not proof of absence is an admission the assertion has no evidence. Producing flimsy evidence would be better than pointing out the absence of evidence fallacy.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Robert Sacchi

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