What Is fallacy and how do you know if your argument is a good one?

Fallacy is invalid or incorrect reasoning that has the appearance of validity. It is a misleading, erroneous or fallacious argument that tries to be psychologically persuasive and convincing . From Latin, the term comes from fallacia which means deception . Every fallacy violates some logical rule by arguing outside of it, attacking and discrediting the person instead of defending a certain position with reasoning. That is , fallacious, erroneous or incorrect arguments are used directed at the person who argues instead of focusing them on the position they are trying to defend.

The word “fallacy” is a common word that we have probably all used or heard in everyday language. Usually, we use it to indicate the falsehood of some statement or statement. However, for those who do logic, the concept of fallacy contains something more complex and precise. Why is it important to know this concept? Next, we explain why it is convenient for you to know what a logical fallacy is and why it is important.

Fallacies can be understood as errors in reasoning.

– Fallacies can be of two types: formal and informal.

– Formal fallacies occur when we reach certain conclusions through logically invalid reasoning.

– Informal fallacies can be detected by their content or by the purpose of the fallacious argument used. The arguments in these fallacies may be valid or invalid, but they do not support our conclusions.

Reasoning and fallacies

What is a fallacy? According to Irving Copi, author of one of the most influential books on logic since the middle of the last century, ” An introduction to logic, ” logicians often use this term to designate typical errors in reasoning. These errors, Copi explains, exhibit recognizable patterns and can be identified and even named. But what is an “error of reasoning”?

As the City University of New York professor Graham Priest explains in his book ” Logic: a very short introduction, ” when we try to persuade others of something, we give them reasons. In the same way, when we try to know the truth about something, we rely on reasons. Logic, Priest says, is the study of what counts as a good reason to believe something and also why it is a good reason. Let’s look at an example.

In this example, conclusion C is supported for two reasons: p1 and p2. Logicians usually call these reasons premises (that is why we call them p1 and p2) and conclusion to the inference made from these. The set of premises and conclusion is called an argument. The previous example is a good reasoning, because the premises will necessarily lead us to the conclusion . If indeed Rome is the capital of Italy and the plane landed in Rome, then there is no way that the plane did not land in Italy.

Now, as Copi explains, our arguments contain reasons. However, not all reasons are good reasons. In the same way, the reasons we use do not always lead us to the conclusion we reached. These cases represent errors of reasoning and constitute fallacies.

The validity of an argument

One of the ways in which logicians evaluate whether an argument is good or bad is by analyzing its validity. What is the validity of an argument? The first thing we must know is that the validity of an argument does not really depend on the falsehood or truth of the statements we use, but on its logical structure . That is, it is appropriate for us to draw a conclusion from certain premises. Let’s look at an example.

In Example 1, it is fair to conclude that Socrates is mortal from the first two premises. In example 2, on the contrary, it is not legitimate to reach this conclusion. Why? For while all men are mortal and Socrates is mortal, this does not necessarily exclude the possibility that Socrates is not a man. In fact, “Socrates” could be the name of the neighbor’s pet. Thus, although in Example 2 the first premise is true and the second is true (obviously pets are also fatal), the conclusion does not necessarily follow from them.

In that sense, we can define the validity of an argument in the following way: an argument is valid when there is no way that the conclusion is not true if its premises are also true . In this way, we can have a valid argument, but with false premises.

In this case, if the premises were true, then the conclusion would also have to be true: the argument is valid. However, the first premise is false: not all dogs have four legs (there are lame dogs). This argument, however, is not a fallacy because the logical structure of the reasoning is valid.

Since logic is not concerned with the truth of our beliefs, but with the way in which we reason, from a merely logical point of view, there would be no problem with this argument. Of course our conclusion is false; However, the structure of the reasoning is adequate and this is what logic is concerned with.

Now, to understand the different types of fallacies it is necessary to know that there are different types of arguments.

Argument types

Both Priest and Copi make a difference between deductive and inductive arguments. The former are arguments in which the premises necessarily lead to the conclusion (with a valid logical structure), while the latter are arguments that, although they do not necessarily lead us to the conclusion (and are invalid), can give us good results. reasons to believe the conclusion.

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