The definition of fallacy comes from the Latin “fallaci” and whose translation is literally “deceit”, in itself it can be defined as an argument that is apparently valid, however it is not. It can be used intentionally, with the aim of manipulating someone, however there are other fallacies that are committed without any intention, and that can occur either due to ignorance or carelessness on the part of a person. It should be noted that on many occasions these arguments can be very persuasive as well as subtle, making it very difficult to detect them.

what is a fallacy

The meaning of fallacy that is most often used is a deception, error or falsehood that is intended to harm a third party, and thereby obtain some benefit. The argumentative fallacy as such is a property of a fallacious thing, which means that they have the ability and will to lie, in order to cause another person an error. Therefore it can be said that a synonym of this word is lie.

Within the field of logic, it refers to those arguments that seek to defend something that has no validity. If the definition of fallacy is taken into account, it can be said that it is related to disloyalty, dishonesty, etc., in order to benefit from another individual through deception. Therefore, a valid synonym for this word is falsehood.

For its part, in economics, there is the term “composition fallacy”, a concept that indicates that it is an argument that seeks to infer that a whole is true, based on the variation of some of its elements, such as, ” the pieces of a television will not break if they fall to the ground, for that reason if the television falls to the floor it will not break”, it can be said that this is a fallacy in composition, since there will always be the possibility that said pieces can be broken. damage if they fell to the ground.

There are some definitions that focus on the different flaws in the logic of this, these contribute to having a better point of view regarding the meaning of fallacy, an example of this can be seen in the definition of fallacy seen as an invalid deductive element or that, failing that, it has little deductive support. However, this definition has a drawback and it is the fact that there are lies that are based on deductively acceptable arguments, and their fault lies in another element, such as a request for principles or a false dilemma.

This definition has as a point in favor that it does not include false dilemmas, nor requests for principles as fallacies, but it does have a negative point and that is the fact that it includes a large number of legitimate elements as fallacies.

Likewise, a term that must be taken into account when talking about this term is sophism, two terms that despite being similar are not the same, since sophism is the term used to describe a false reason that it has the appearance of truth. An example of sophistry can be “yesterday I studied all day, therefore today I will have a good grade”.

Main types of fallacy

Since ancient times these have been divided into different types, however there is the possibility that many of them are still unknown to man, due to the existence of small cultures that have not been fully studied. Aristotle, for his part, classified them into non-verbal and verbal. However, it should be noted that there are many ways to classify logical fallacies, but since there is no specific way as such, in this case it will be done according to their membership, which divides them into: formal and non-formal.

formal fallacies


This type of logical fallacies are detected through critical analysis from logical reasoning. This means that there is no link between the premise and the conclusion, although the pattern of reasoning is characterized by being logical, it is always incorrect.

To better understand the meaning of formal fallacy, the following example is presented, which shows a clear pattern that this type follows:

  • “Dogs have four paw. Tito is a dog and therefore Tito has four legs.»

This variety of fallacies can be detected if the substitution of elements that are part of the premises of the symbols is used, to later analyze if the reasoning is coupled with the logical rules. It should also be noted that the formal ones have subtypes:

Fallacies of bad reasons

Also known as Argumentum ad Logicam, the meaning of the fallacy of bad reasons is based on the idea that the conclusions are not good, since the arguments are not either.

Appeal to probability: through previously acquired knowledge and probability, what seems logical is taken for granted, since it is very probable.

Fallacy of the masked man

Also known under the term of intentional fallacy, this requires that one of the parties be replaced, in this way when both things are exchanged, they are similar and it can be assumed that the argument used is valid.

Undistributed middle term

This does not cover in its three principles the total number of members of the category or group.

informal fallacies

It is the second type of logical fallacies and they are characterized by the fact that they depend directly on the content itself and perhaps also on the objective of the reasoning. These can be presented more easily than formal ones, and have a large number of subtypes:

ad hominem fallacy

It is known as ad hominem fallacy to those arguments that attack the interlocutor himself instead of attacking the affirmations and position of the same. The strategy of the ad hominem fallacy is the disqualification of the interlocutor’s position, disqualifying his defender for it.

For example, if a person uses the argument “you say that stealing is bad, however you practice it”, he is using an ad hominem fallacy, since what he wants is to refute the fact that stealing is bad, attacking the proponent. If a bandit defends the idea that stealing is bad, it may be something hypocritical on his part, however, it does not mean that the falsity or the truth of said proposition will be affected.

ad baculum fallacy

Its main characteristic is the use of force, abuse of position or threat, for example:

1. A: “Boys shouldn’t go out at night due to insecurity”

2. B: “He’s my son and I don’t care about your opinion, that’s why he can continue going out at night so he can enjoy his youth”

In this example you can see how party B abused his position as the boy’s father.

Fallacy ad verecundiam

It is based on the defense of a true thing, since it is expressed by a person who has the necessary knowledge in the area.

popular fallacy


In this case the premises are considered true, since they have the support of many individuals who have the same opinion regarding a particular thing. How, for example, “a cell phone sales business is considered by a large number of people as the best cell phone sales chain.”

Fallacy ad ignorantiam

Known in that way to the argument that defends the falsity or reality of a proposition because I do not know how to prove otherwise.

post hoc fallacy

Based on the mistaken idea of ​​whether one thing happens after another, it means that the first act is a cause of the second, this type of reasoning is the cause of a large number of beliefs and superstitions.

examples of fallacy

question of principle

This is characterized by containing conclusions regarding an argument that must be proven explicitly or implicitly within the parameters available for such action. Therefore it is considered a circular way of reasoning, where the conclusion focuses on the premise. Example, “I am your older brother and I am right, because older brothers always have it”.

Assertion of the consequent

This ensures the reality of a premise through a conclusion, opposing the so-called linear logic, example “whenever it rains it is cold, then if it is cold it is because it is raining”.

hasty generalization

This affirms a conclusion based on few premises, and extends the reasoning to the largest number of cases. Example, “my mom likes tomato, my brother likes tomato. The whole family loves tomatoes”, which can be a lie or defamation, that is, a synonym for fallacy.

Frequently Asked Questions about Fallacy

What does the word fallacy mean?

It is known as the error, deception or falsehood that is used to harm a person without realizing it. This is usually used to obtain something that could not be obtained in any other way than through lying.

What are fallacies for?

Fallacies are characterized by having an appearance of correct reasoning, however, they turn out to be the opposite, since they have the purpose of deceiving through persuasion and conviction.

What are fallacies in advertising for?

Fallacies are common in advertising and are structured so that the consumer is attracted to the brand or product promoted based on deception. Despite not being the most appropriate way, it is the one that sometimes gives the best results.

What is the fallacy of relevance?

It is one where a group of people repudiate or judge the opinion expressed by another, based on the personality, appearance, physical features, ideologies and background of the same, these being inconsequential characteristics within the subject in question.

What are formal and informal fallacies?

Formal fallacies are characterized by errors that go unnoticed, while informal fallacies seek to convince by providing irrational ideas.