The 14 types of logical and argumentative fallacies

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

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

What are fallacies?

A fallacy is a reasoning that, despite looking like a valid argument, is not..

It is, therefore, a line of reasoning that is erroneous, and the inferences that are presented as a product of these cannot be accepted. Regardless of whether the conclusion reached through a fallacy is true or not (it could be by pure chance), the process by which this has been reached is defective, because it violates at least one rule logic.

Fallacies and psychology

In the History of Psychology there has almost always been a tendency to overestimate our ability to think rationally, being subject to logical rules and showing consistency in our way of acting and to argue.

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

It has been in the last decades when the idea that irrational behavior is at the center of our lives has begun to be accepted, 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 the extent to which we move by emotions and impulses that are not or not at all rational. This fact is that we have had to develop a kind of catalog of fallacies to try to make them have little weight in our daily lives.

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

The main types of fallacies

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

Below you can see a compilation of the best known fallacies. Since there is no single way to classify them to create a system of types of fallacies, in this case classified according to their belonging to two relatively easy-to-understand categories: 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 us to reach the conclusion that has been reached, regardless of whether the premises are true or not.

In other words, irrational ideas about how the world works are appealed to to give the impression that what is being said is true.

1.1. Fallacy ad ignorantiam

The ad ignorantiam fallacy attempts to take the veracity of an idea for granted simply because it cannot be shown to be false..

The famous meme of Flying Spaghetti Monster It is based on this type of fallacy: since it cannot be shown that there is no invisible entity made up of spaghetti and meatballs that is also the creator of the world and its inhabitants, it must be real.

1.2. Fallacy ad verecundiam

The ad verecundiam fallacy, 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 their author was a neurologist.

1.3. Ad consequentiam argument

This type of fallacy tries to show that the validity or not of an idea depends on whether what can be inferred from it is desirable or undesirable..

For example, an ad consequentiam argument would be to assume that the chances of the military giving a coup in a country are very low because the opposite scenario would be a severe blow to the citizenship.

1.4. Hasty generalization

This fallacy is a generalization not supported by sufficient data.

The classic example is found in the stereotypes about the inhabitants of certain countries, who can lead to the fallacious thinking, for example, that if someone is Scottish he must be characterized by his stinginess.

1.5. Anecdotal fallacy

As its name indicates, the problem with anecdotal fallacy is that we start from anecdotal observations to reach conclusions. Here the problem is not so much the lack of information, as occurs in hasty generalization, but rather the poor quality of the information from which one starts.

For example, when we try to estimate the efficacy of a type of psychotherapy based on our personal experience, we are falling into this type of fallacy, since neither We have not even adopted a scientific methodology to extract information in a systematic way about the effectiveness of this procedure, nor have we taken into account our biases.

1.6. Straw man fallacy

In this fallacy, the opponent's ideas are not criticized, but rather a caricatured and manipulated image of them..

An example would be found in a plot line in which a political formation is criticized for being nationalist, characterizing it as something very close to what was Hitler's party.

1.7. Post hoc ergo propter hoc

It is a type of fallacy in which it is taken for granted that if one phenomenon occurs after another, it is caused by it, in the absence of more evidence to indicate that this is the case..

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

1.8. 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 he does not take care of his personal image.

However, you have to know how to distinguish this type of fallacy from legitimate arguments referred to the characteristics of a specific person. For example, appealing to the lack of university studies of a person who talks about advanced concepts of physics quantum can be considered a valid argument, since the information given is related to the subject of the dialogue.

1.9. Midpoint fallacy

In the midpoint fallacy, a supposedly equidistant position is adopted regardless of whether all the information considered is equally valid and consistent.

For example, if we are informed that a person has invented a new type of pseudo therapy and they ask us if that practice should be included in the public health system, we would be falling into the fallacy of the middle point if we assume that health services should give the same importance as the forms of therapy already offered and that have demonstrated their effectiveness.

1.10. Fallacy tu quoque

In this kind of informal fallacy, It creates the illusion of refuting an argument by pointing out that the person proposing it is not acting in a manner consistent with that idea..

It can be understood as a variant of the ad hominem fallacy, since it tries to disguise criticism of the person from criticism of her reasoning.

1.11. Composition fallacy

This error when reasoning occurs when we try reach conclusions about an element based on observations about one of its parts. For example:

• Sodium explodes on contact with water.
• Salt contains sodium.
• Salt explodes on contact with water.

2. Formal fallacies

Formal fallacies are not because the content of the premise does not allow the conclusion reached, but because the relationship between the premises makes the inference 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 into our reasoning irrelevant and unnecessary ideas, but because there is no coherence in the arguments that we use.

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

2.1. Denial of antecedent

This type of fallacy starts from a conditional of the type "if I give him a gift, he will be my friend", and when the first element is denied, it is incorrectly inferred that the second is also denied: "if I don't give him a gift, he won't be my friend."

2.2. Affirmation of the consequent

In this type of fallacy, one also starts from a conditional, but in this case the second element is affirmed and it is incorrectly inferred that the antecedent is true:

"If I pass, I uncork the champagne."

"I uncork the champagne, so I approve."

2.3. Undistributed middle term

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.

Example:

"All French are European."

"Some Russian is European."

"Therefore, some Russian is French."