8º. Beware of fallacies

2020/11/12 Elhuyar Zientzia



A fallacy is an invalid or misleading reasoning, with a direct and credible appearance. The worst of the fallacy is that sometimes it is difficult to identify. There are many fallacies and you have to be careful with them. Below are some frequently used fallacies:


Arguum ad ignoratiam:

The fallacy Arguum ad ignoratiam recognizes that ignorance of evidence against something is a favorable evidence. In other words, he tries to defend information by arguing that there is no evidence to prove otherwise.

By using this fallacy, therefore, the arguments are not based on knowledge, but on lack of knowledge, that is, on ignorance. For example: “No one has shown that there is life on other planets, so there is no existence,” “Ghosts exist, because no one has shown that they do not exist,” “No one can show that astros do not affect our lives, so astrological predictions are true,” etc.


Arguu ad verecundiam:

It is common for a person to disseminate certain information, whether or not certain, using their prestige or power. In this way, it can happen that someone takes advantage of their reputation or authority to spread personal opinions on a subject (usually polemical) and thwart real information (for a particular interest or not).

When someone with political, economic, or cultural authority speaks or thinks about something outside their scope, it is easier to question the credibility of what they say, but what happens when the authority is scientific? Is the credibility of what it says guaranteed? Not always, and to guarantee the credibility of the information, it is very important to know the opinion of the scientific community about what the expert said.

Be careful, therefore, with the information provided by someone with a certain prestige or authority. And it is that a person's fame or authority does not make absolute truth.

The above paragraphs can relate to a type of fallacy, known as Argument ad verecundiam, which means that, to defend the credibility of an information, someone who knows (or has some authority) is mentioned in this matter, without giving other reasons. For example: “He is right, he studied biology and knows a lot about it.” This person may be right in what he says, but not because he studied biology.


Arguum ex populo:

If when reading information people agree with what is said in it, they receive many lichens, but that does not. This is closely related to another fallacy called arguum ex populo. Ex populo arguments are used in populist discourses, in politics, in the media and in daily debates, using phrases such as: “And I don’t say it, everybody says it,” “Most people have my same opinion,” “Everyone knows that’s it,” etc.

This fallacy is based on the improper use of logic, since things are never true because someone knows them (or because everyone knows them), but because they coincide with the proven evidence. Therefore, be careful with the information that have many likes or become trending topic, since the number of followers does not guarantee their credibility.


Cum hoc ergo propter hoc:

The arguments, when completed with data from measurable parameters, are more credible, but these data must also be credible, so the data used to argue any assertions are also correct. Scientific data do not serve at all without statistics and to be acceptable they must meet minimum requirements.

Correlation is a statistical concept that must be used with great care when formulating an argument, since correlation does not always mean causality. Causality refers to the cause and effect of a phenomenon, in which something directly causes a change of something else. The correlation is the comparison or description between two or more variables. Therefore, correlation does not always mean causality, that is, that two phenomena occur simultaneously does not mean that one has produced the other.

There is another associated fallacy, known as “Cum hoc ergo propter hoc”, which says that when we have two events that occur together, one is the cause of the other.

For example, let's analyze the following argument: Many drug users have psychiatric problems and many with psychiatric problems consume drugs. Therefore, drug use generates psychiatric problems. Although the conclusion may be true, the argument is false, since the correlation between drug use and psychiatric problems cannot guarantee the cause-effect relationship. Drug use can lead to psychiatric problems, but it can also happen that psychiatric problems cause drug use, or that both are due to a third, or that there is no relationship between the two facts and it is a coincidence.

When two events occur at a time, it may be tempting to admit that one causes the other, but, in addition to statistical correlation, more information is needed to properly conclude that there is a causal relationship between one and another event.


Arguum ad hominem:

Whoever uses the fallacy known as arguum ad hominem does not present the right reasons, but rather rejects the person who defends an affirmation, or attacks it for its characteristics or ideas and tries to deny the credibility of the affirmation.

Many of the political debates that can be seen on television are a sign of this: the Tertullians who want to express their reasons by shouting and despising the arguments of others often use the ad hominem argument to deal with the opinions of the opposing party, without criticizing their own arguments, without objectivity, and all of them marked by the ideological tendencies of the speakers.

The deputy of the PP, Celia Villalobos, for example, spoke of the deputies of Podemos and its aspect, since they were away from the suit and tie that until then was habitual in the Congress of Deputies. In particular, deputy Alberto Rodríguez Rodríguez said: “It gives me the same thing to wear rakes, but to carry clean so as not to get infected.” With these statements on television, Villalobos, instead of criticizing with arguments the opinions of the deputy of Podemos, tried to despise his appearance.

But not only do they look on the TV. In our day to day it is also customary, for example, to use the word “feminazi” to argue against the feminist movement. In this way, instead of expressing with respect the reasons why they oppose the demands and opinions of feminists, they are assaulted trying to condemn the people who are in their favor. That is, a feminist assimilates herself to a Nazi, trying to slander the individual (feminist) and the movement (feminism).


A critical thinker should know how to listen and analyze others' arguments about information and defend their opinions through evidence-based arguments. He will try to identify fallacies in the arguments of others and avoid using fallacies in the arguments he will use to defend his ideas.


To download the document click here.

Interesting link: https://falacias.escepticos.es/