In public discourse, research and academic writing, logical fallacies should always be avoided because they invalidate conclusions and arguments. Unfortunately, it is easy to commit such logical fallacies ourselves.
Simply, a logical fallacy is erroneous reasoning that looks sound (Schagrin, et al, 2021). It can be either a seriously incorrect argument, or an incorrect conclusion based on such arguments.
It is important to know how to spot logical fallacies to avoid making them, and to detect, invalidate, or correct arguments made by others. You need not have a degree in philosophy to have a solid basis for logical and sound reasoning. By knowing common logical fallacies, you can arrive at conclusions that are reliable and as close to the truth as possible.
Logical fallacies come in many types. This article will discuss only the most common ones.
Logical fallacies are divided into two main types. Formal fallacies contain errors in the logical structure of an argument, and only its logical structure, while informal fallacies contain errors in the premise or assumptions, form, and content (material and verbal) of the argument (Schagrin, et al, 2021) regardless of logical structure.
A recent analysis of medical fallacies can be found in a paper titled, “Fallacies in medical practice: Renin-angiotensin-aldosterone system inhibition and COVID-19 as a Paradigm” in the Hellenic Journal of Cardiology.
It states that “In emergency situations, such as during the coronavirus disease 2019 (COVID-19) pandemic, medical community looks for quick answers and guidance. Under these circumstances, experts instead of admitting ignorance, feel obliged to give an answer, often pressurized by political or other authorities, even when such an answer is unavailable. Under these circumstances, publications based on fallacious reasoning are virtually unavoidable. (Triposkiadi, Dean Boudoulas, Xanthopoulos, and Harisios, 2020).”
Common tactics in arguments, especially when one is losing, are the ad hominem (‘to the person’ or ‘against the person ‘) and Tu Quoque (‘you too’) attacks (Merriam-Webster, n.d.). Neither of these addresses the actual question but instead attacks the other person‘s character, intentions, experience, consistency, or qualifications.
– “You say that college education should be free, but you’re not that smart.“
For example, Tu Quoque
– “You say that smoking should be banned on campus, but you are yourself a smoker, are you not?”
In the first example, the opposing side clearly attacks the person saying he/she is not smart, and the second example questions the other person’s consistency—both avoid the issues being presented.
When one tries to persuade us that their stance is what the majority likes, wants, or thinks, it is called Argumentum ad populum or Appeal to the People (Dowden, n.d.).
Everybody likes Coca-Cola more than Pepsi, so you should like Coke, too!
Just because everybody likes something or something is popular with the majority doesn’t mean it’s good for us or should we choose it too, without further evidence.
Nobody got vaccinated at all when vaccines were first introduced, so don’t trust vaccines!
This can work the other way when trying to discredit something by stating that nobody wants it. Yes, nobody wanted to get vaccinated early on because they did not understand the science behind it, but it is an accepted fact now that vaccines work and save lives.
Circular reasoning or “circulus in probando,” also “begging the question,” occurs when one’s argument has a conclusion that is significantly similar to the premise (APA,2020).
The sky is orange at sunset because it is reddish and yellowish in hue.
The words orange and reddish/yellowish are just the same colors, so the reasoning is flawed because the premise and conclusion are just saying the same thing.
The death penalty is never justified because taking a human life is always wrong.
Sure, many would disagree with the death penalty, but this statement does not provide any reason why it is not justified. A better argument could be made by citing other facts such as conviction bias against the poor, actual crime rates, etc.
A straw man is a weak or imaginary opposition set up to be easily refuted (Merriam-Webster. (n.d.)). In other words, instead of addressing a question, one will present a distorted or weakened form of the opponent’s stance (the straw man) and then attack that straw man. One presents the other side’s stances INACCURATELY, and that inaccurate representation is what is attacked instead of the actual stances.
It is very difficult to discern the straw man in certain situations, especially when scientific facts are used, but distorted cleverly.
The Theory of Evolution states that complexity in the universe increases over time, but the Second Law of Thermodynamics states that the universe tends toward chaos or disorder, and therefore, towards decreased complexity. Thus, the Theory of Evolution is not supported by, and goes against, the laws of thermodynamics, and, is therefore, false.
This is very cleverly-worded, but distorts the Second Law—yes, the universe tends towards disorder, just as the Second Law of Thermodynamics states, but it is not impossible to have complex biological life because of energy. Energy can allow organisms to develop, grow, and evolve, and circumvent—not disobey—the Second Law. The proof is that we actually see complex life around us and in geological time requiring energy, and evolving towards more complexity.
The straw man is the distorted view that the Second Law of Thermodynamics is an absolute rule that cannot be circumvented. It can be—by energy stored in ATP, produced by mitochondria, triggering life’s constant evolution towards complexity.
Post hoc ergo propter hoc literally means, “after this, therefore because of this” (Merriam-Webster. (n.d.)).
If event A occurred, it must have caused event B to happen.
I talked on the phone for four hours, and now I feel sick. So, talking on the phone made me sick.
Maybe it was, but it doesn’t discount the fact that other things might have made him sick, like a virus spreading in his house, the food he ate before talking on the phone, or some other cause.
Assuming that chronological sequence implies a first event to have caused the second event is fallacious.
Appeal to Ignorance or Argument from Ignorance is a type of fallacious reasoning that can take one of two forms:
1) Taking a statement as false because we don’t know if the statement is true.
2) Taking a statement as true because we don’t know if the statement is false. (Dowden, n.d.)
1) God does not exist because there is no evidence that proves His existence.
2) God exists because there is no evidence that disproves His existence.
In both cases, the premise is (incorrectly) assumed to be correct because of absence of evidence to the contrary.
We can see that they have opposing conclusions, but committed the same logical fallacy!
We often refer to authorities in specific fields for scientific or legal advice, but appeal to authority means to refer to a person who is an expert in a certain field without additional evidence or proof.
This type of fallacious reasoning can take on several forms, like misquoting the authority, misrepresenting the authority as an expert in a field he/she is not an expert in, when the authority is not trustworthy, and when a given subject has much disagreement among authorities (Dowden, n.d.)
1) The election was rigged because Donald Trump said so.
2) Dr. X said that vaccines don’t work, so I don’t believe in vaccines.
In example 1, Trump is not an authority on elections, he certainly is not trustworthy, and there is no disagreement among experts that the elections were fair and not rigged.
In example 2, some so-called “authorities” are not true experts in immunology, medicine, and epidemiology, so their opinions on the efficacy (or alleged inefficacy) of vaccines are not valid.
It is often very effective to distract a crying child with a shiny object. Just point to your Christmas tree ornament or a mirror.
A red herring is a statement or question that is meant to divert attention from the topic or issue being discussed. Its etymology is quite interesting—herring fish turned red when they were salted and cured, and were so smelly that dog owners used them to distract their hunting dogs from the scent of their quarry (Merriam-Webster. (n.d.)). It is an apt analogy for a distraction meant to avoid the topic.
Person A: The police should not be so indiscriminate in killing unarmed black people.
Person B: What about the hundreds of thousands of white US soldiers who died in WW2? These numbers are much higher than a few black deaths! All lives matter!
The argument that there are more white lives lost is a red herring that distracts from the real issue of police brutality, and the rest of the sentence almost sounds convincing. Almost. That’s what a red herring does—it distracts from the real issue.
The fallacy of equivocation is when a term or phrase can have several meanings, but is used ambiguously in an argument. Often one part of the argument uses one meaning but another part uses a different meaning, conflating the two to create a false conclusion. Sometimes, a single term or phrase is used, but has a different meaning for the speaker than for the audience.
1) You say you’re an ethical person, but your work ethic is so bad!
2) “This government does not torture people “. (The United States does not torture). – George W. Bush, 2007.
In example 1, the word “ethical,” meaning behaving honestly and fairly, was conflated with the word “ethic” or “work ethic,” one’s dedication to his/her job. The implication of the conclusion was that the person being addressed is not ethical because he/she has a poor work ethic! However, poor work ethic at a company does not necessarily equate to dishonesty and being a bad person. Maybe he/she was a whistleblower who did not like working for the company.
In example 2, George W. Bush said the US does not torture people with conviction because, in his mind, waterboarding was not torture. Maybe he, like us, thinks of torture as the medieval types of torture that were very brutal. Nonetheless, waterboarding is torture (OHCHR 2017).
False analogies utilize a valid comparison of two things in aspects they are alike, and falsely introducing another comparison that they must be alike in other aspects too.
These analogies are easy to make and are sometimes difficult to detect because we get hooked on the first analogy and generally accept it as true, and preconditions our mind to accept the second, and false, analogy (APA, 2022).
1) Dogs are very much like humans. Dogs respond well to discipline. Therefore, it is also good to discipline people.
2) A complex pocket watch must have been designed intelligently by a watchmaker, and life and the world are also complex. Thus, they must also be the product of an intelligent designer. (paraphrased from William Paley (Archie,2006).
Example 1’s first sentence is generally true in some aspects, and so is sentence 2. Yes, we discipline our dogs so they won’t misbehave or bark at our relatives. But sentence 3 implies that humans should be disciplined harshly like dogs, sometimes physically when they get out of hand. There is a false equivalency in this analogy, and the conclusion is certainly false.
In example 2, complexity in itself is something that fills us with awe, thereby the ease by which the argument convinces people. However, it is a fallacy because the analogy of a watchmaker making a pocket watch to a designer designing the universe Is not a congruent one. For instance, there are so many ‘flaws’ in the natural world and the universe that design does not seem to be the norm. Rather, as evolution shows, change is mostly random and obeys natural selection—the survival of the fittest. Life is full of disease and suffering that design almost implies cruelty. The universe itself is full of black holes and dying stars.
Note: This does not prove or disprove that there is or is no God. It is safe to say that the logic is flawed and the argument is a fallacy.
Evoking emotions in arguments are quite valid, but NOT when emotions are the ONLY source of support for an argument.
Appeal to emotion is a technique that attempts to influence an audience by manipulating their emotions rather than using logic to win an argument. In other words, factual evidence and logic are absent in the arguments that appeal to emotion (Dowden, n.d.).
1) You should eat your vegetables. Think of all the hungry, starving children in Africa!
2) I think I deserve a raise! My child is in the hospital, prices of goods are increasing, and I have only one source of income!
Example 1 is a great way to make your kids eat vegetables, but someday they’ll really wonder why you compared them to starving children, and they’ll just pig out on meat. It would have been better if we explained to them the health benefits of eating vegetables.
Example 2 is also known as appeal to pity, quite effective in certain situations. However, justification for a raise usually follows the accountants’ assessment of a company’s solvency, and the employee’s performance is usually the basis for a raise, not his/her economic situation.
The either-or fallacy or false dichotomy argument is stated to make the other person choose only between two alternatives even if there may be more than one choice, or that both choices are valid. The trick is to make a statement appear to have only two mutually-exclusive choices—and that one has to choose either A or B.
1) Which one is it – nature or nurture – that influences who we eventually become?
2) You should get married or you will be alone for the rest of your life!
In example 1, nature (genetics) and nurture (the environment) are presented as the only factors that affect a person’s development and personality, and one of them has more influence than the other. Asking us to choose which of the two really determines who we become ignores the scientific fact that BOTH genes and the environment affect us, and more importantly, the INTERACTION between our genes and our environment is a third factor that also affects us. These THREE factors, not one, not two—determine who we will become.
In example 2, marriage and being alone are represented as the only two choices one can have, but it ignores the fact that it is also possible to have a life partner without getting married, or being in a civil marriage as opposed to a church marriage, or having pets as companions.
Logical fallacies still occur even in medicine! If you want to get into the top 10 medical schools or excel in public health, you need to pay attention to some modern medical logical fallacies in disease diagnosis.
There is a common disorder of the inner ear called Meniere’s disease, which causes dizzy spells (vertigo) and hearing loss (Mayo Clinic , 2022). Did you know that doctors still don’t have a clear definition of Meniere’s disease? It is a well-identified disease but certain associated terms—suspicious, uncertain, probable, atypical, and pseudo-Meniere—are still unclear and lead to differences in diagnosis.
Vestibular migraine and vestibular paroxysmia are also vague terms that have caused much confusion in the field that one doctor, J. Magnan, described the situation as an “appeal to ignorance” because of lack of contrary evidence (Magnan, 2018). Hopefully, the doctors sort this out by agreeing on more etiological evidence.
Let us avoid fallacies and communicate accurately and clearly!