Logical fallacies: a general overview

“Applying logic to potentially illogical behaviour is to construct a house on shifting foundations. The structure will inevitably collapse.”

Stewart Stafford

Logical fallacies are like landmines; easy to overlook until you find them the hard way. By definition, a logical fallacy is an error in reasoning that may seem impressive and convincing but in truth it does prove nothing. Fallacies can be either illegitimate arguments or irrelevant points, and are often identified because they lack evidence that supports their claim. 

One of the most important components of learning in college is academic discourse, which requires argumentation and debate. Argumentation and debate inevitably lend themselves to flawed reasoning. Many of these errors are considered logical fallacies. They are commonplace in the classroom, in formal televised debates, and perhaps most rampantly, on any number of internet forums.

In this article, we are going to explore five fallacies that anyone can encounter everywhere and everytime.

Ad Hominem

This translates as “to the man” and refers to any attacks on the person advancing the argument, rather than on the validity of the evidence or logic.  It’s is one thing to say that I don’t agree with you, but it’s another thing to say that I don’t like you, and you are wrong because I don’t like you;  evil people often make valid claims, and good people often make invalid claims, so separate the claim from the person.  You must remember that the validity of an argument has utterly nothing to do with the character of those presenting it.  

A very common exempel of Ad Hominem is ” Tu quoque” or “You also” which refers to a claim that the source making the argument has spoken or acted in a way inconsistent with the argument.

For exemple, let’s say a student and a teacher are arguing about the Educational System. The student says: “I think we should try to improve the outdated methods of teaching. They are not effective anymore.” However, the teacher replies: “You students are just lazy. You don’t work hard and then you blame the system for having a hard time.”

The ad hominem accusation of the student is relevant to the narrative and is not fallacious. On the other hand the attack on the student (that is the student blaming the system and not working hard) is irrelevant to the opening narrative. So the teacher’s tu quoque response is fallacious.

Argument From Authority

It is simply the use of the source’s authority to justify the validity of the argument.

Sometimes fallacious arguments from authority are obvious because they are arguments from false authorities. Supermodels who push cosmetics or pro athletes pushing home loans or even sports equipment are likely false authorities: first, we don’t know the supermodel or athlete uses the product at all, and second we can assume that the supermodel is beautiful without the product and the pro athlete was successful without the equipment…would.

This fallacy can be difficult to avoid because we generally have good reason to believe authority or expert figures.  Frequently, authorities do make accurate claims. However, it is important to realize that the validity of an argument has nothing to do with the person making the claim.

In other cases, they are not obvious and they are hidden under layers of other logical fallacies which makes the source of that authority powerful enough to resist any criticism or skepticism. If the church believes that the earth is flat, then it is flat! Because the church said so!

Slippery Slope

  A course of action is rejected because, with little or no evidence, one insists that it will lead to a chain reaction resulting in an undesirable end or ends. The slippery slope involves an acceptance of a succession of events without direct evidence that this course of events will happen.

This is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,…, X, Y, Z will happen, too, basically equating A and Z. So, if we don’t want Z to occur, A must not be allowed to occur either. Example:

” Today late for ten minutes, tomorrow late for an hour, and then someday you will simply cease to show up. “

In this example, the speaker is assuming that the listener will keep coming late further and further with every passing day which is not necessarily true. Maybe at that day, the listener had something urgent that disturbed his usual routine.

Genetic Fallacy

The genetic fallacy arises whenever we dismiss a claim or argument because of its origin or history.

This conclusion is based on an argument that the origins of a person, idea, institute, or theory determine its character, nature, or worth.

“Why should I listen to her argument? She is a woman, and we all know women are flakes.”

In this example the author is dismissing an argument because of the origin of its source. Remember that an argument is not necessarily wrong even if the source is bad.

Genetic accounts of an issue may be true, and they may help illuminate the reasons why the issue has assumed its present form. However, they are not conclusive in determining its merits.

Weasel Words or Glittering Generality

It denotes the use of ambiguous words and phrases intended to create the false impression that a vague or meaningless statement is, to the contrary, both specific and informative.

This is the use of words so broadly defined – such as “love” or “freedom” or “rights” or “patriotism” etc. etc.  – as to become essentially meaningless. no one, and I do mean no one, on this planet, does not value love, freedom, or rights, and most everyone is a patriot of one kind or another. It’s the “one kind or another” nature of these words that makes them essentially pointless: they mean something different to everyone, and so their use in an argument frequently means nothing.  “Love”, for example, refers to both sexual passion and the nature of God or divine virtue. 

Technically, their use is probably not a fallacy. Yet, their use tends to move an argument no where while inciting deep emotional responses. Thus, they are rhetorically useful and logically distracting.

According to a 2009 study of Wikipedia, the most weasel words could be divided into three main categories:

  1. Numerically vague expressions (for example, “some people”, “experts”, “many”, “evidence suggests”)
  2. Use of the passive voice avoid specifying an authority (for example, “it is said”)
  3. Adverbs that weaken (for example, “often”, “probably”)


This article lays out some of the most common logical fallacies you might encounter. You should be aware of them in your own discourse and debate. I hope that I added something new to your knowlegde!

Logical fallacies are like tricks or illusions of thought, and they’re often very sneakily used by politicians and the media to fool people. Don’t be fooled! 

I may expand more in this topic because I think it is of an utmost importance for us, Engineers!

Nameless Soul

He stumbled upon an epiphany, very suddenly and quite by accident. Here we stand, feet planted in the earth, looking to the sky and searching for heavens...but might the truth be very near us, only just within ourselves?

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