Discover 10 Types of Logical and Argumentative Fallacies

Logical and argumentative fallacies are errors in reasoning that can affect our understanding and decision-making.

Although often used interchangeably, logical and argumentative fallacies have key differences in terms of their nature and the context in which they are generally applied.

That is, logical fallacies relate to the structural form and internal validity of an argument, while argumentative fallacies focus more on how content and context are used to persuade or convince, frequently in a misleading or non-rigorous manner.

In this article, we will explore the 10 most common types. Knowing and recognizing these fallacies is crucial in order to identify and refute invalid arguments.

The 10 Types of Logical and Argumentative Fallacies

Non-formal Fallacies

Non-formal fallacies are errors in reasoning that affect the conclusion of an argument. A common example is the false cause fallacy, where it is assumed that, just because two events are correlated, one causes the other. For example, believing that the use of umbrellas causes rain. Another fallacy is hasty generalization, which occurs when a conclusion is drawn based on an insufficient sample. For example, claiming that all cats are bad because one scratched a person.

1. Ad Ignorantiam Fallacy

The ad ignorantiam fallacy occurs when something is assumed to be true simply because it has not been proven otherwise. This fallacy is based on the lack of evidence to assert the truth of something, which does not guarantee the validity of the assertion.

A common example of this fallacy is to claim that aliens exist only because no one has demonstrated that they do not exist. Another case is to believe in the existence of ghosts just because there is no evidence that they do not exist.

To avoid falling into the trap of the ad ignorantiam fallacy when reasoning, it is important to look for proof and solid evidence instead of relying on the lack of evidence. One should question whether there is actually evidence to support the claim, rather than assuming something is true just because no one has proven otherwise.

2. Ad Verecundiam Fallacy

The ad verecundiam fallacy, or appeal to authority, occurs when a person's position or status is used as evidence for the veracity of their argument, rather than presenting solid evidence. This fallacy can be avoided by making arguments based on concrete and solid evidence, rather than simply relying on someone's reputation or authority.

A clear example of this fallacy is when a celebrity chef claims that a weight-loss product is effective, without offering scientific proof. People will trust his word because of his authority on the culinary subject, but solid evidence does not support his claim.

In a political debate, this fallacy can also be observed when a politician boasts of having the endorsement of a renowned figure, rather than presenting his own argument based on facts and data.
By avoiding the ad verecundiam fallacy, a more informed debate based on concrete evidence is encouraged, rather than blindly relying on one person's authority.

3. Ad Hominem Fallacy

The ad hominem fallacy is a logical error in reasoning in which the person presenting an argument is attacked instead of addressing the content or validity of the argument itself. In other words, instead of refuting or discussing someone's ideas or claims, one attacks the person themselves.

To avoid falling into the ad hominem fallacy, it is crucial to focus on presenting valid and relevant arguments rather than personally attacking the arguer. It is important to address the issue at hand and not divert attention to irrelevant personal characteristics.

For example: "I don't think Marta's arguments about economics are valid, she has always been very conservative in her investments". Here, instead of evaluating Martha's argument on economics based on its content, it is dismissed because of her personal investment behavior, which has no direct bearing on the validity of her argument.

4. Post Hoc Ergo Propter Hoc

The post hoc ergo propter hoc fallacy is committed by assuming that because one event happened after another, the first was the cause of the second. To avoid falling into this fallacy, it is important to look for more evidence to support the causal relationship between the events. This involves analyzing other possible factors that could have contributed to the outcome, as well as considering the possibility that the correlation between the events is just a coincidence.

It is crucial not to assume causality simply because two events are related in time. It is necessary to critically examine the available evidence and look for strong arguments to support the proposed causal relationship. Instead of assuming a direct connection, it is essential to keep an open mind and consider different possible explanations.

A clear example of this fallacy would be to say that the crowing of the rooster causes the sun to rise, just because the crowing always occurs before the sun rises. In reality, the relationship between the two events is merely correlational and there is no evidence of direct causality. Another example would be to assume that the consumption of green tea causes weight loss, just because some people who have consumed it have experienced a decrease in weight.

5. Straw Man Fallacy

The straw man fallacy is a dishonest tactic of misrepresentation in argumentation. It consists of caricaturing or distorting the opponent's position, thus creating a weaker or more easily refuted version of his original argument. This fallacy manifests itself in debates or discussions when a person attacks a distorted version of his opponent's position instead of addressing his actual argument.

A clear example of this fallacy would be, "Green advocates just want to stop our country's economic progress." In this case, you are misrepresenting the position of green advocates by portraying them as enemies of progress, rather than discussing their actual arguments about the importance of environmental sustainability.

It is crucial to recognize and avoid the straw man fallacy in communication and argumentation, as it undermines intellectual honesty and makes it difficult to reach mutual understanding. By recognizing this type of argumentative dishonesty, we can improve the quality of our debates and discussions, fostering a more constructive and enriching exchange of ideas.

6. Ad Consequentiam Argument

The ad consequentiam argument consists of trying to justify an idea or assertion based on the desirable or undesirable consequences that would follow from it, rather than on solid evidence or grounds. This type of fallacy focuses on persuading the audience by appealing to emotions and possible consequences, rather than logic and evidence.

An example of this type of fallacy would be arguing against the legalization of marijuana based on possible negative consequences for society, such as increased crime, rather than presenting concrete evidence of the actual effects of legalization in other countries.

This fallacy can be identified in a debate or speech when one constantly appeals to the consequences of an idea, instead of presenting solid arguments. The aim of this type of argument is to influence the persuasion of the audience, manipulating their emotions and making them accept an idea not because of its validity, but because of the supposed consequences that would follow from it.

7. Hasty Generalization

Hasty generalization occurs when a conclusion is drawn based on a sample that is too small or unrepresentative. To avoid this error, it is important to base statements on sufficient evidence, rather than relying on stereotypes or illogical assumptions.

An example of a hasty generalization is saying that you don't like an artist's music when you have only heard one song, or thinking that you won't get along with a person's family just because you don't have a good relationship with that person.

It is crucial to gather relevant facts and statistics before making generalized statements about a group of people or a situation. Additionally, it is essential to avoid using language that reinforces stereotypes and prejudices, as this can lead to racist or sexist statements. Instead of generalizing, it is better to use specific and precise terms that reflect the diversity and complexity of reality. In doing so, we can avoid falling into the trap of hasty generalization and promote a more informed and respectful dialogue.

Formal Fallacies

Formal fallacies are logical errors that occur when establishing an inaccurate or invalid relationship between the premises of an argument, which generates incoherence in the conclusion presented. These fallacies do not refer to the falsity of the arguments themselves, but to the lack of coherence between the premises and the conclusion.

An example of formal fallacy is the fallacy of affirmation of the consequent, which consists of incorrectly inferring a premise from a conclusion. For example: "If it rains, the ground will be wet. The ground is wet, therefore, it has rained". This statement assumes that if the ground is wet, the only possible cause is rain, ignoring other possible explanations.

Another common formal fallacy is the fallacy of negation of the antecedent, which consists of incorrectly inferring a conclusion from a negated premise. For example: "If you study hard, you will pass the exam. You have not studied hard, therefore, you will not pass the exam". This statement assumes that the only condition for passing is to study hard, ignoring other variables that may influence the result.

8. Denial of the antecedent

The fallacy of the denial of the antecedent is a common error in logical reasoning that occurs when someone assumes that if the premise of a statement is not true, then the conclusion is not true either.

There are two types of fallacies involving the denial of the antecedent: the denial of the formal antecedent and the denial of the informal antecedent. An example of the first one would be: "if it is not a bird, then it does not fly", which is incorrect since there are things that are not birds but can still fly. An example of the second one would be: "If you don't study, then you will fail the exam", which is also wrong since there are other reasons why someone could fail an exam that are not necessarily linked to not studying.

To identify and correct this fallacy in critical thinking, it is important to pay attention to the premises and check whether they really justify the conclusion. It is also useful to question the connection between the premise and the conclusion, looking for additional evidence or considering other possible scenarios.

9. Undistributed Middle Term

The fallacy of the undistributed middle term occurs when two terms are assumed to have something in common only because they share a third term. To avoid this fallacy, it is important to identify all the premises of a reasoning and make sure that each one is correctly represented in the argument.

A clear example of this fallacy would be, "All birds have wings and all airplanes have wings, therefore, all birds are airplanes." In this case, it is assumed that just because they share the characteristic of having wings, birds and airplanes are the same, which is incorrect.

In a syllogism, premises are fundamental to avoid the fallacy of the undistributed middle ground. If any premise is not included in the reasoning, there is a risk of falling into this fallacy. It is crucial to cover all premises to ensure that the argument is valid and does not contain logical errors.

10. Affirmation of the Consequent

The fallacy of consequent affirmation occurs when a second element in a sentence is confirmed, and it is incorrectly inferred that the previous premise or antecedent is true. For example, if someone says: "If John is a good student, then he will get good grades", and then concludes: "John got good grades, therefore he is a good student", he would be falling into this fallacy.

This fallacy is identified by observing whether the conclusion is based solely on the assertion of a second element, without considering other possible explanations. It is important to avoid this type of reasoning in order to maintain logic in arguments, as it can lead to erroneous conclusions.

Other Types of Fallacies

While logical fallacies are common in arguments and debates, there are other types of fallacies that also affect the way we think and reason:

- Relevance fallacies: these fallacies occur when information or arguments are introduced that are not relevant to the topic at hand. For example, in a debate on nutrition, a participant might divert attention by talking about the price of food instead of its nutritional value.

- Fallacies of ambiguity: occur when vague or ambiguous language is used that can be interpreted in multiple ways. An example would be, "I read that the solution is not clear," where the term solution could refer to either an answer to a problem or a liquid mixture.

- Assumption fallacies: These fallacies occur when an argument is based on unproven or erroneous assumptions. For example, stating that a person cannot give an opinion on education because they are not a teacher wrongly assumes that only teachers have valid knowledge on the subject.

- Evidence suppression fallacies: occur when relevant data or evidence that contradicts the conclusion is deliberately ignored. For example, when it is argued that a product is completely safe, omitting studies that indicate possible side effects.

- Sunk cost fallacy: this fallacy refers to continuing with a company or project because of the significant investment made, regardless of future prospects. For example, continuing to invest in an unprofitable venture simply because a lot of money has already been invested in it.

- Circular fallacy: Occurs when the argument returns to the starting point without offering real evidence. An example would be to say, "Laws are fair because they are created by a fair system," which is a circular statement that offers no real basis for the fairness of the laws.

Understanding logical and argumentative fallacies is essential to debating effectively and mastering the art of public speaking. If you want to hone your communication skills, we invite you to explore this public speaking course, where we give you the tools to find your voice and learn how to address an audience.

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