Common Logical Fallacies and How to Identify Them

Types of Logical Fallacies

Logical fallacies can be divided into two main types: formal fallacies and non-formal fallacies.

Formal Fallacies

Formal fallacies are defects based on the logical form of reasoning rather than the content of the argument.

Non-Formal Fallacies

Non-formal fallacies are categorized by the nature of their error. We can identify three primary kinds:

• Fallacies of ambiguity: These occur when arguments are based on ambiguities of language.
• Material fallacies: These occur when one takes advantage of knowledge on a subject to manipulate others.
• Fallacies of relevance: These occur when one provides arguments to convince through emotion or distraction rather than using logical methods.

Fallacies of Relevance and Membership

• Argumentum ad populum: This is the attempt to win approval for a conclusion by arousing the passions and enthusiasm of the audience, without giving logical reasons or evidence. It is the preferred resource for advertisers and demagogues.
• Argumentum ad baculum (The Stick): This is based on threats and is divided into two types:
  • Threat category: Subtly showing that if the other person does not accept your conclusions, you will use your power against them.
  • Catastrophic consequences: The speaker lists a series of tragic consequences that will result from not following what they propose.
• Argumentum ad hominem (Directed against the person): An attempt to discredit the interlocutor directly instead of addressing their arguments:
  • Ad hominem attack: Discrediting the speaker by their nature or identity (e.g., gender, race, or social status).
  • Ad hominem circumstantial: Discrediting the speaker by suggesting they have a personal interest in the matter being discussed.
• Argumentum ad verecundiam (Appeal to authority): An argument that relies on the statements of famous people or someone who is an authority to us, even if they are not experts on the subject.
• Argumentum ad ignorantiam: Used when confirming the certainty or falsity of an issue simply because nobody has proven otherwise.
• Argumentum Tu quoque (You too): When faced with an accusation regarding our behavior, we respond by reminding the accuser that they have done the same thing.

Other Common Fallacies

• Ex populo: Defending an idea or behavior based on the fact that most people do it.
• Fallacy of complex questions: Trapping the speaker through questions that include a series of allegations taken for granted.
• Fallacy of false cause: When one relies on a mere coincidence between two events to establish a relationship of cause and effect.
• Fallacy of circular argument (or Petitio principii): When the demonstration uses the same conclusion as a premise, albeit implicitly.