Logical fallacies are errors in reasoning that can undermine arguments and lead to bad decisions. They are often found in politics, media, advertising, and daily discussions.
Recognizing and understanding these fallacies enhances critical thinking and argumentative skills, helping you to identify flaws in reasoning, construct more persuasive arguments, and make better choices.
- What is a logical fallacy? A logical fallacy is the use of erroneous reasoning that renders an argument invalid or unsound.
- Understanding fallacies helps you think better. Studying fallacies sharpens your ability to critically analyze information, enabling you to identify, avoid, or challenge misleading arguments in various contexts.
- Apply your understanding to others and yourself. Spotting fallacies isn’t just about winning arguments. It will help you assess your thinking and avoid inaccurate or unsupportable conclusions.
What Is an Argument?
Before we dive into fallacies, let’s first quickly look at what an argument exactly is.
As you know, in everyday situations an “argument” refers to a situation where people are having a (heated) disagreement. In philosophy and logic, however, it means something more; it’s a set of statements — premises and a conclusion — made for or against a particular idea, theory, or position.
☔️ As an example, consider the following:
“Every time there is rain coming, my joints start aching. My joints started aching. So, there must be rain coming.”
This is an argument that has two premises and a conclusion. If we break it down, it would look like this:
- Premise 1: Every time there is rain coming, my joints start aching.
- Premise 2: My joints started aching.
- Conclusion: There must be rain coming.
In essence, the premises of an argument are meant to provide us with enough reasons to accept the conclusion. The cause for most (but not all) arguments failing is that they don’t offer strong enough premises to achieve this.
Types of Fallacies
A logical fallacy is the use of erroneous reasoning that renders the argument either invalid or unsound.
As Dave Kemper summarized in his book Fusion: Integrated Reading and Writing:
A logical fallacy is a false statement that weakens an argument by distorting an issue, drawing false conclusions, misusing evidence, or misusing language.Dave Kemper et al., Fusion: Integrated Reading and Writing. Cengage, 2015.
As mentioned at the beginning, they may be committed unintentionally due to carelessness or lack of a better understanding of them, however, often they are committed deliberately in order to persuade someone.
The word “fallacy” comes from the Latin word fallacia, which translates to “deceit”, “deception,” or “trick”. These words describe them quite accurately: they are deceivingly persuasive and are frequently used to trick or fool people.
Moreover, classifying specific fallacies accurately is challenging because of the large variety of their application and structure. There are, in fact, hundreds of them and more than two dozen types and sub-types. However, they are mainly divided into two broad categories: formal and informal fallacies.
The origin of logical fallacies goes all the way back to Ancient Greece and, more specifically, to the well-known Greek philosopher Aristotle (384 – 322 BC), who laid the foundation by identifying the first thirteen fallacies in his On Sophistical Refutations. In his work, he didn’t only aim to show how one can win debates by making logically valid and sound arguments but also demonstrated how to refute various claims.
Formal fallacy, also known as a non sequitur and deductive fallacy, refers to a flaw in the structure of a deductive argument.
Deductive arguments intend to provide a necessarily true conclusion given that the premises are also true. Hence, its validity is dependant on the structure of the argument. Furthermore, they can be valid or invalid, or sound or unsound:
A valid deductive argument is one that cannot simultaneously have true premises and a false conclusion. Otherwise, it’s invalid.
A sound deductive argument is one that is valid and all of its premises are true. Otherwise, it’s unsound.
One common type of formal fallacy is the affirming the consequent, and its logical form looks like this:
- Premise 1: If A is true, then B is true.
- Premise 2: B is true.
- Conclusion: Therefore, A is true.
☔️ An example would be:
- Premise 1: If it’s raining, then the streets are wet.
- Premise 2: The streets are wet.
- Conclusion: Therefore, it’s raining.
There is a clear error here because the conclusion doesn’t follow from the given premises; it doesn’t necessarily mean it’s currently raining, even if the streets are indeed wet. As such, the truth of the premises doesn’t logically guarantee the truth of the conclusion, making the argument fallacious.
Another non sequitur would be denying the antecedent. It’s quite closely related to the previous one, but here the mistake arises because it incorrectly deduces the inverse of the conditional statement:
- Premise 1: If A, then B.
- Premise 2: Not A.
- Conclusion: Therefore, not B.
- Premise 1: If he’s a human, then he has a brain.
- Premise 2: He isn’t a human (he’s a dog).
- Conclusion: Therefore, he doesn’t have a brain.
Similarly, this argument is invalid due to a flaw in the structure; even though both premises are true, the conclusion is still false.
Informal fallacies deal with the non-structural flaws in arguments. Essentially, they deal with all the other errors that formal fallacies don’t. Furthermore, although they typically occur in inductive arguments, they may also apply to deductive ones.
An inductive argument is one that is meant to provide strong enough premises to support a probable truth of the conclusion. As such, the success of an inductive argument relies on the evidence supporting the conclusion, that is, on the strength of its premises.
👶 To give you an example, consider the following:
- Pregnancy tests are around 98% accurate.
- Chloe got a positive result on a pregnancy test.
- Chloe is most likely pregnant.
This is a reasonable inductive argument: Since the accuracy rate of the pregnancy test is as high as 98%, it is justified to assume that Chloe is pregnant.
🚗 Another example:
“I’ve had my car for 5 years, and it has never broken down. Therefore, I don’t have to worry about it breaking down tomorrow.”
Assuming it’s true that the car has never broken down in 5 years, then it would be unlikely that it will break down tomorrow; the premise is strong enough to warrant a probable truth of the conclusion.
Now, due to the fact, there is almost an unlimited number of ways the premises can actually fail at backing up the conclusion, there is a very large variety of identified informal fallacies. As such, they are organized into three sub-categories: fallacies of ambiguity, fallacies of relevance, and fallacies of sufficiency.
Fallacies of Ambiguity
These types of fallacies are caused by a lack of clarity. Some examples include:
- Accent fallacy — placing unusual stress or emphasis on certain words to change the meaning of a sentence.
- Composition fallacy — asserting that if something is true of the parts, it must be true of the whole.
Fallacies of Relevance
Fallacies of relevance attempt to persuade by using non-logical means. They often use emotional appeals as evidence for the conclusion. For instance:
- Appeal to pity — using the feeling of pity to persuade.
- Appeal to force — using force or threat of force to persuade.
- Straw man — distorting an opponent’s argument in order to make it easier to attack.
Fallacies of Sufficiency
In essence, fallacies of sufficiency occur when the evidence fails to provide, in one way or another, adequate support for the conclusion.
- Hasty generalization — drawing a conclusion from an insufficient sample size.
- False dilemma — presenting only two possible choices when in fact, more alternatives exist.
- Weak analogy — drawing a connection between two things, even though the connection is insufficient for making any conclusions based on it.
Benefits of Studying Logical Fallacies
Logical fallacies are a common occurrence in debates and discussions everywhere — from politics to media to advertising to philosophical debates. They are an important aspect of argumentation, as well as logical and critical thinking.
Ideally, whenever we are expressing our opinions to other people and, in effect, attempting to persuade them that we are right, we should be doing it with sound reasoning and relevant facts. However, in reality, this doesn’t happen most of the time; people argue for things without proper reasons and end up using various tactics to bypass logic — for reasons such as lack of evidence and personal gain.
This applies to both verbal and written persuasion. As William R. Smalzer explains here:
There are three good reasons to avoid logical fallacies in your writing. First, logical fallacies are wrong and, simply put, dishonest if you use them knowingly. Second, they take away from the strength of your argument. Finally, the use of logical fallacies can make your readers feel that you do not consider them to be very intelligent.William R. Smalzer, Write to Be Read: Reading, Reflection, and Writing, 2nd ed. Cambridge Univ. Press, 2005.
More precisely, some of the benefits you may gain from studying logic and fallacies include:
- It’ll help you develop your vocabulary and form better, more persuasive arguments of your own, which, in turn, will make you seem more credible and can help you reach your goals.
- You’ll be better able to evaluate other people’s arguments and spot and counter poor reasoning.
- It’ll help you defend yourself from people who wish to influence your beliefs, values, or actions in a way that may be against your self-interests.
Examples of Logical Fallacies
Now, let’s take a closer look at some of the most common types of fallacies.
Ad hominem occurs when someone attacks the person behind an argument instead of addressing the actual merit of their argument. The attacks may be directed toward the person’s character, morals, background, intelligence, or reputation.
👉 Here are a couple of examples:
- “You didn’t even finish high school; therefore, we shouldn’t listen to your opinion about anything!”
- Mike: “There are so many Earth-like planets out there that there must be intelligent life on some of them.”
Jenny: “What would a moron like you possibly know about this?”
Red herring fallacy happens when one derails the original issue to a different, irrelevant one. It’s a deliberate attempt to move the focus away from a certain topic in order to gain an advantage.
🎣 An example would be:
Joanna: “Why did you buy that new fishing rod? It exceeds the monthly budget that we both agreed upon.”
John: “Well, because it was on sale. I had to buy it now.”
John commits the red herring here because he tries to distract Joanna from the real issue, which is the fact that he exceeded the budget that they had both agreed upon.
Straw man occurs when an opponent attacks a distorted version of the original argument that they themselves created. More accurately, it’s an intentionally misrepresented or exaggerated version of the issue that better suits the arguer’s agenda.
👉 For Example
- John: “I believe sport hunting is immoral.”
Michael: “So you want us all to be vegetarians because animals are more important than people?!”
- Kim: “I think our company should allocate a larger portion of the budget to customer support because we are struggling in that area.”
Andy: “We’ll go bankrupt if we spend all our money on customer support.”
Bandwagon fallacy, also known as “appeal to popularity”, is when something is claimed to be good or true solely because it is popular. In other words, it’s based on the assumption that a majority’s opinion must be correct.
🍔 For Example
- “Intermittent fasting is the most popular way to lose weight right now. Thus, it must be the right way to do it.”
- “McDonald’s is the best fast food restaurant in the world, they have served 100 billion people worldwide.”
The fallacy of slippery slope works by taking the argument from a relatively small first step to an ultimate conclusion via a number of inaccurate connections. The conclusion is typically some sort of extreme.
🎮 For Example
- “If I let my child play video games, she will not do her homework, her grades will suffer, and she won’t be able to go to college.”
- “If we legalize gay marriage, next people will want to legalize polygamy.”
Appeal to Nature
Appeal to nature is based on the belief that if something is natural, it must be good or the right thing to do, and conversely, if something is unnatural, it must be bad and should be avoided.
🌺 For Example
“Herbal medicines are natural, unlike antibiotics and other modern medicines. Therefore, herbal medicines are better for you.”