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Common Fallacies in Speaking and Writing … and What to Do about Them

Ubiquity, Volume 2024 Issue May, May 2024 | BY Philip Yaffe

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Volume 2024, Number May (2024), Pages 1-7

Communication Corner: Common Fallacies in Speaking and Writing … and What to Do about Them
Philip Yaffe
DOI: 10.1145/3663588

Each "Communication Corner" essay is self-contained; however, they build on each other. For best results, before reading this essay and doing the exercise, go to the first essay "How an Ugly Duckling Became a Swan," then read each succeeding essay.

Expository (non-fiction) speaking and writing are almost always about trying to affect the audience's opinion or perception of something. The best communicators do so by presenting logical explanations supported by verifiable facts. Less diligent communicators do so by presenting logically fallible explanations supported by questionable facts. Sadly, they often do so not because they are dishonest, but rather it is because they themselves are unaware that this is what they are doing.

Ever since this series of essays began, the primary objective has been to help non-professional writers and speakers better express themselves in print or at the lectern. To achieve this, the essays have focused on fundamental principles and techniques of effective oral and written expression.

One thing of critical importance has not yet been mentioned—logical fallacies. These are lapses of coherent thinking. No matter how well you present yourself, if the essence of what you say is flawed, your effect will be diminished, or perhaps even countermanded.

Just what is a logical fallacy?

By the simplest definition, a logical fallacy is a gap in one's thinking that, on inspection, calls into question or invalidates the point the speaker or writer is trying to make.

Logical fallacies are difficult to spot because there are so many of them. In fact, well over 100. Fortunately, they tend to fall into two categories: 1. fundamental fallacies, and 2. ancillary fallacies. Herein, we will examine some of them so that you can get a better idea of what they look like—and why, on inspection, they fail.

But first an amusing anecdote.

When I was a student at UCLA studying mathematics and physics, I took a course in verbal logic. I noticed the textbook made numerous references to the classic story of Alice in Wonderland by Lewis Carroll. At the time, my only familiarity with the story was via the inimitable feature-length cartoon by Walt Disney. However, I saw nothing in it worthy of academic study, so I decided to read the book. That's when everything changed.

The author Lewis Carroll's real name was Charles Ludwig Dodson, who was a professor of mathematics at Oxford University. If you know what you are looking for, you will find examples of fundamental logical fallacies sprinkled throughout the book.

One day I was sitting outside UCLA reading Alice in Wonderland while waiting for a bus. A little old lady passing by happened to notice what I was reading. A quizzical look came over her face. She then looked up at the university. Finally, she walked away shaking her head. I don't know what she was thinking, but I imagine it was nothing good.

Editor's note: Lewis Carroll (Ludwig Dodsen) in fact wrote two books, Alice's Adventures in Wonderland (1865) and its sequel Through the Looking-glass (1871). Together they have become known as Alice In Wonderland.


Shifting the burden of proof fallacy,

"Classic logical fallacies" are those most often mentioned by people who study and teach about such things. Additionally, there is a much longer list of other fallacies of less primal importance. There is no official list of classic logical fallacies; however, most lists of classic fallacies seem to include most of the following. You should pay close attention to them in listening or reading what other people say and write—and even closer attention in what you say and write.

Throughout the following text, you will frequently see the word "argument." It is used in the sense of debating, i.e. person A proposes something and gives reasons for the proposal, while person B opposes the proposal and gives reason why it should not be adopted. It in no way implies bickering, slandering, name-calling, and other fruitless distractions from fruitful discussion and decision-making.

Strawman fallacy
This fallacy occurs when a person over-simplifies or misrepresents another's position on a subject in order to make it easier to undermine or attack. Instead of addressing the actual proposition, the exchange degenerates into a fruitless, often intemperate distraction. For example, John proposes repainting the living room. Mary responds by accusing John of wanting to endanger the family's finances by recklessly dipping into their savings in order to satisfy a frivolous, self-indulgent whim.

Bandwagon fallacy
This fallacy relies on the mistaken belief that just because a large number of people already believe something to be true does not automatically make it true. For example, for centuries, even millennia, most people believed that the Earth is flat. Some still do, although the evidence strongly points to our planet being a round (or more specifically an oblate spheroid).

Appeal to authority fallacy
This fallacy occurs when it is claimed that a proposition must be correct because a well-known authority says it is. But if it is said by an authority, how can it be fallacious? Quite easily. The fact that someone is a reputed authority in one field doesn't automatically make them an authority in another. For example, Albert Einstein was unquestionably a non-peril authority on the nature and structure of the universe. But would this have given him any authority to decide who was the better painter, Rubens or Picasso? Or the best way to make pancakes? Or virtually any other subject? Clearly not.

You can legitimately appeal to an authority to help decide a question in which that person has real expertise. However, appealing to the authority of someone who has no expertise in the question under discussion only muddies the waters.

False dilemma fallacy
This common fallacy (all too common) occurs when a complex issue is presented as a grossly oversimplified proposition that can be reduced to a question of clearly right or clearly wrong. It must be true, or it must be false; nothing else is possible.

In reality, most contentious issues are rather more subtle than this. They are often on a spectrum of possibilities, whereas the false dilemma fallacy asserts that there are only two possibilities, which are mutually exclusive. Thus, whichever side wins the debate, reducing the discussion to "either this or that" is inherently wrong. Worse, it precludes the possibility of reframing the issue in a different way, in turn preventing the possibility of compromise.

For example, "We can either adopt the proposal or do nothing. But doing nothing will only let the problem fester and grow. The proposition must be approved."

Hasty generalization fallacy
This fallacy occurs when people draw all-encompassing conclusions based on insufficient evidence. A common way of labeling this fallacy is "jumping to conclusions."

For example, "Two members of my team have become more engaged employees after taking public speaking classes. That proves we should have mandatory public speaking classes for the whole company to improve employee engagement."

Slothful induction fallacy
The slothful induction fallacy is the exact opposite of the hasty generalization fallacy. It occurs when all the available evidence strongly points to a particular conclusion; however, the conclusion is dismissed by attributing it to coincidence or some other irrelevant factor.

For example, "I know the project was supposed to show a profit within six months, but we are still making losses after two years. However, this is the result of unexpectedly poor weather and a shortage of the necessary materials. The project itself is still sound and needs no revision. So, let's end the discussion here."

Correlation equals causation fallacy
If two things appear to be correlated, i.e. there is a relationship between them, this doesn't necessarily mean that one of them is caused by the other. They may have a cause-and-effect relationship, but equally, they may not. They may both be the result of a third factor not yet discovered or properly taken into consideration.

For example, "When I woke up this morning, the street in front of my house was wet, so I thought that it must have rained during the night. Later I discovered that the street-cleaning crew had just passed, leaving the street wet with water."

It is quite true that whenever it rains, the streets get wet, so this would be a very good guess; however, it is not true that this is the only way the streets get wet. In short, there is a very high correlation between rain and wet streets. But wet streets are not proof that it rained. This of course is a very trivial example. However, for more weighty propositions, the mistaken idea that correlation equals causation can lead to serious, damaging, unwanted consequences.

Anecdotal evidence fallacy
This fallacy devalues or eschews logical evidence in favor of examples from personal experience. This fallacy occurs when one values personal experience or the experience of a handful of others over a mass of accumulated verified data. To rely on anecdotal evidence overlooks the fact that one (possibly isolated) example can't stand alone as definitive proof of a greater premise.

For example, "We changed the color scheme of our website and the number of visits doubled. So, changing the color scheme can really boost a website's success. Therefore, we should change our color scheme at least once or twice a year."

Burden of proof fallacy
If a person claims that something is true, it is their responsibility to demonstrate the truth of their claim, i.e. "X is true because of…." It is not the responsibility of someone else to demonstrate the claim is not true. This is what is meant by shifting the burden of proof.

For example," Aliens from outer space have visited the Earth. Can you prove that this has never happened? Of course not. So, I win." "The Loch Ness monster is real. Can you prove that it isn't real? Of course not. So, I win." Etcetera, etcetera, etcetera.

Belief from personal incredulity fallacy
This fallacy consists of insisting that something must be true because it is just too hard to imagine any other credible possibility. But whether or not one can imagine another possibility has no bearing on the truth of a claim. This fallacy is often seen in discussions of philosophy and religion. "I know it because I know it because I know it."

For example, "The universe must have been created by an intelligent agent. I just cannot imagine that it just popped into existence as posited by the Big Bang Theory." "Alien life forms must have visited the Earth. With billions and billions of potentially inhabitable planets in the universe, I just cannot imagine that never happened."

Caveat. It is important not to commit the opposite fallacy of asserting that because something cannot be successfully demonstrated that it must be false. Claiming that something is false must also be proved. The best that can be said is that at the moment it is still an open question requiring further investigation.

Appeal to tradition fallacy
This fallacy consists of saying "This is how we have always done it, so this is how we should continue doing it." Having done something over a long time, even centuries, may be a valid argument for continuing to do it.

For an extensive list of ancillary logical fallacies, visit


I began this essay by recounting an amusing anecdote (at least I think it is amusing) that happened to me when I was an undergraduate. Here is another anecdote about my time at UCLA that is anything but humorous. It is in fact quite sad.

One day I attended a practice debate being put on by a class in public speaking. The topic was contentious. In 1958, as a first step toward a full test-ban treaty, the United States and the Soviet Union (USSR) temporarily suspended nuclear testing. In September 1961, the USSR suddenly resumed testing. The topic of the debate was "Should the U.S. also resume nuclear testing?"

The spokesman for the "No" position presented copious amounts of data to demonstrate that the American lead in nuclear technology was already so far superior to that of the USSR that resumption of testing was definitely not needed, including an unequivocal statement from President Kennedy's own chief scientific advisor to this effect. The debate speaker made the additional point that by not resuming nuclear testing, the U.S. would achieve a major propaganda victory over the USSR.

The speaker for the "Yes" position then came to the lectern and said something to the effect, "Now let's see who is opposed to the U.S. resuming nuclear testing. Well, there's Mao Tse Tung, Fidel Castro, Ho Chi Minh—and my opponent." He then sat down and said nothing more.

When the audience was asked who had won the debate, the vote went almost unanimously in favor of the "Yes" position. The professor was furious; he could hardly contain himself. "After all we have been studying, the vast majority of you really believe that the Yes position, appealing only to prejudice, actually did a better job? I'm appalled!" I don't remember what else he said, however, it wasn't pleasant.

But there we were. A large group of students at a prestigious university had rejected a reasoned, well-documented argument in favor of a simple appeal to prejudice. I went away shaking my head in disbelief.

This happened more than 60 years ago, and I am still shaking my head. It seems that the situation not only hasn't improved but has actually gotten worse. I fear for the future.


Philip Yaffe was born in Boston, Massachusetts, in 1942 and grew up in Los Angeles, where he graduated from the University of California with a degree in mathematics and physics. In his senior year, he was also editor-in-chief of the Daily Bruin, UCLA's daily student newspaper. He has more than 40 years of experience in journalism and international marketing communication. At various points in his career, he has been a teacher of journalism, a reporter/feature writer with The Wall Street Journal, an account executive with a major international press relations agency, European marketing communication director with two major international companies, and a founding partner of a specialized marketing communication agency in Brussels, Belgium, where he has lived since 1974. He is the author of more than 30 books, which can be found easily in Amazon Kindle.

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