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The 10 types of logical and argumentative fallacies

The 10 types of logical and argumentative fallacies

June 17, 2024

Philosophy and psychology are related to each other in many ways, among other things because both address in one way or another the world of thought and ideas.

One of these points of union between both disciplines is found in relation to the logical and argumentative fallacies, concepts used to refer to the validity (or lack of it) of the conclusions reached in a dialogue or debate. Let's see in more detail what they are and what are the main types of fallacies.

What are fallacies?

A fallacy is a reasoning that despite resembling a valid argument, it is not .

It is, therefore, a line of reasoning that is wrong, and the inferences that arise as a result of these can not be accepted. Regardless of whether the conclusion reached through a fallacy is true or not (it could be by chance), the process by which it has been reached is defective, because it violates at least one logical rule.

Fallacies and psychology

In the history of psychology almost always there has been a tendency to overestimate our capacity to think rationally, being subject to logical rules and showing coherence in our way of acting and arguing.

With the exception of certain psychological currents such as the psychoanalytic one founded by Sigmund Freud, it has been assumed that the healthy adult human being acts according to a series of motives and reasonings that can be easily expressed and that usually fall within the framework of rationality. The cases in which someone behaved irrationally were interpreted either as a sign of weakness or as an example in which the person does not know how to identify the true reasons that motivate their actions.

It has been in the last decades when s e has begun to accept the idea that irrational behavior is located at the center of our lives , that rationality is the exception, and not the other way around. However, there is a reality that has already been giving us a clue as to how far we are moving by emotions or impulses that are not very rational or not at all. This fact is that we have had to develop a kind of catalog of fallacies to try that these have little weight in our day to day.

The world of fallacies belongs more to the world of philosophy and epistemology than to that of psychology, but while philosophy studies fallacies in themselves, from psychology one can investigate the way in which they are used. The fact of seeing the extent to which false arguments are present in the discourses of people and organizations gives us an idea of ​​the way in which the thinking behind them is more or less tied to the paradigm of rationality.

The main types of fallacies

The list of fallacies is very long and there may be some of them that have not yet been discovered because they exist in very minority or poorly studied cultures. However, there are some more common than others, so know the main types of fallacies can serve as a reference to detect violations in the line of reasoning where they are.

Below you can see a compilation of the most well-known fallacies. Since there is no single way to classify them to create a system of types of fallacies, in this case they are classified according to their membership into two categories that are relatively easy to understand: non-formal and formal.

1. Non-formal fallacies

Non-formal fallacies are those in which the reasoning error has to do with the content of the premises . In this type of fallacy what is expressed in the premises does not allow to reach the conclusion that has been reached, regardless of whether the premises are true or not.

That is, appeals to irrational ideas about the functioning of the world to give the feeling that what is said is true.

1.1. Fallacy ad ignorantiam

In the fallacy ad ignorantiam is tried to take for granted the veracity of an idea for the simple fact that it can not be shown to be false .

The famous meme of the Flying Spaghetti Monster is based on this type of fallacy: as it can not be shown that there is no invisible entity formed of spaghetti and meatballs that is also the creator of the world and its inhabitants, it must be real.

1.2. Falacia ad verecundiam

The fallacy ad verecundiam, or fallacy of authority, links the veracity of a proposition to the authority of the person defending it, as if that provided an absolute guarantee .

For example, it is common to argue that Sigmund Freud's theories about mental processes are valid because his author was a neurologist.

1.3. Argument ad consequentiam

In this type of fallacy is intended to show that the validity or otherwise of an idea depends on whether what can be inferred from it is desirable or undesirable .

For example, an argument ad consequentiam would be to assume that the chances that the army will take a coup in a country are very low because the opposite scenario would be a serious blow to citizenship.

1.4. Rushing Generalization

This fallacy is a generalization not based on sufficient data .

The classic example is found in the stereotypes about the inhabitants of certain countries, which may lead one to think fallaciously, for example, that if someone is Scottish, they should be characterized by their stinginess.

1.5. Fallacy of straw man

In this fallacy the ideas of the opponent are not criticized, but a caricatured and manipulated image of these .

An example would be found in a line of argument criticizing a political party for being a nationalist, characterizing it as something very close to what Hitler's party was.

1.6. Post hoc ergo propter hoc

It is a type of fallacy in which it is assumed that if one phenomenon occurs after another, it is caused by it, in the absence of further evidence to indicate that this is so .

For example, one could try to argue that the sudden rise in the price of the shares of an organization has occurred because the start of the season of big game has already reached Badajoz.

1.7. Ad hominem fallacy

By means of this fallacy the veracity of certain ideas or conclusions is denied, highlighting the negative characteristics (more or less distorted and exaggerated) of those who defend them, instead of criticizing the idea itself or the reasoning that has led to it.

An example of this fallacy we would find in a case in which someone despises the ideas of a thinker arguing that this does not take care of his personal image.

But nevertheless, we must know how to distinguish this type of facacia from legitimate arguments referred to the characteristics of a person in particular. For example, appealing to the lack of university studies of a person who talks about advanced concepts of quantum physics can be considered a valid argument, since the information given is related to the topic of dialogue.

2. Formal fallacies

The formal fallacies are not because the content of the premise does not allow to reach the conclusion that has been reached, but because the relationship between the premises makes the inference is invalid .

That is why its failures do not depend on the content, but on the way in which the premises are linked, and they are not false because we have introduced irrelevant and unnecessary ideas into our reasoning, but because there is no coherence in the arguments we use.

The formal fallacy can be detected by replacing all the elements of the premises with symbols and seeing if the reasoning conforms to the logical rules.

2.1. Denial of the antecedent

This type of fallacy is based on a conditional of the type "if I give a gift, it will be my friend" , and when the first element is denied, it is incorrectly inferred that the second element is also denied: "if I do not give him a gift, he will not be my friend".

2.2. Affirmation of the consequent

In this type of fallacy is also part of a conditional, but in this case the second element is asserted and inferred incorrectly that the antecedent is true:

"If I approve, I uncork the champagne."

"I uncork the champagne, so I approve."

2.3. Average term not distributed

In this fallacy the middle term of a syllogism, which is the one that connects two propositions and does not appear in the conclusion , does not cover all the elements of the set in the premises.


"All French is European."

"Some Russian is European."

"Therefore, some Russian is French."

Bibliographic references:

  • Clark, J., Clark, T. (2005). Humbug! The skeptic's field guide to spotting fallacies in thinking (in English). Brisbane: Nifty Books.
  • Comesaña, J. M. (2001). Informal logic, fallacies and philosophical arguments. Buenos Aires: Eudeba.
  • Walton, D. (1992). The Place of Emotion in Argument (in English). The Pennsylvania State University Press.

31 logical fallacies in 8 minutes (June 2024).

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