Concepts of informal logic
Categories: Home -> Philosophy -> Logic
Informal logic is the study of everyday reasoning, focused on how we use arguments in daily life without following the strict rules of formal logic. The study of arguments as they appear in everyday language, in debates, speeches, advertising, journalism, social media, daily conversations, etc. It is concerned with evaluating the quality of arguments in conversations, debates, and common texts, paying attention to fallacies, biases, and persuasion rather than mathematical validity.
Informal logic is concerned with evaluating the reasoning strength of arguments in real contexts, where language is ambiguous, emotional, and full of nuances.
- How people actually reason.
- How to distinguish good from bad arguments in real contexts.
- How to identify fallacies that hide in natural language.
- How to build solid, clear, and persuasive arguments.
Unlike formal logic:
- It does not work with mathematical symbols.
- It does not require rigid syllogistic structures.
- It analyzes context, intention, ambiguity, and persuasion.
What is informal logic for?
-
Evaluating real speeches: Political speeches, journalistic texts, philosophical debates, everyday talks.
-
Detecting fallacies and manipulations: Many fallacies (appeal to emotion, straw man, ad hominem, etc.) are informal.
-
Arguing better: It helps build arguments that are empirical, clear, relevant, and convincing.
-
Critical thinking: It is a fundamental basis in courses on critical thinking, communication, and philosophy.
Informal Fallacies (Common Errors)
A large part of informal logic is devoted to classifying and understanding fallacies, which are arguments that fail at the level of content or context, even though they may sometimes seem superficially valid. Some of the most common include:
| Fallacy | Description | Example |
|---|---|---|
| Personal Attack (Ad Hominem) |
Attacking and discrediting the person instead of the argument | "Economist Juan Pérez says we should reduce public spending, but he is an irresponsible person who has never had a stable job, so his opinion is worthless." "She says we should recycle more, but I saw her throwing a plastic bottle in the regular trash last week. Therefore, don't believe her." "The accused claims to be innocent, but it's obvious he's lying—look at his face." |
| Begging the Question (Petitio Principii) |
The conclusion is already included or assumed in one of the premises (circular reasoning). | "The Bible is the word of God. We know this because the Bible itself says so, and it is truthful." "What this book says is the truth. Why? Because it was written by a very honest author." Creativity is an essential skill in art. Why? Because all art requires creativity." |
| Appeal to Ignorance (Ad Ignorantiam) |
Holding that a proposition is true because it has not been proven false, or that it is false because it has not been proven true. | "No one has proven that ghosts do not exist; therefore, they must exist." "Extraterrestrials must exist. No one has been able to conclusively prove that they do not exist." "Science has not yet discovered exactly how this natural phenomenon works, so it must be the result of a divine power." |
| False Cause (Post hoc ergo propter hoc) |
Assuming that, because event A occurred before event B, A must have caused B. | "Since I changed my diet to style X, I have won the lottery. Clearly, the diet causes good luck." "Since the new administration took control, sales have fallen. Clearly, the new administration is to blame for the drop." "Last year we inaugurated the new production plant and, shortly afterward, it started raining more. The plant is affecting the climate." |
| Appeal to Irrelevant Authority (Ad Verecundiam) |
Citing a person or source as an authority to justify a conclusion, even though that authority is not an expert or is not relevant on the topic. | "My favorite actor says this car brand is the best, so it must be true." "The famous soccer player, who is not a doctor, recommends this new weight-loss pill. It must be effective." "My history teacher says the best investment now is in cryptocurrencies. If he says so, it must be true." |
| Hasty Generalization | Drawing a general conclusion from too few instances or non-representative evidence. | "I met two people from that city and they were rude. Everyone from that city is rude." "My grandfather smoked his whole life and lived to 95. Smoking is not that bad for your health." "I tried two restaurants in this city and the service was terrible. All restaurants here have bad service." |
| False dilemma | Presenting only two options when more exist. | “If you don't support this law, you don't care about security.” “If you don't like current feminism, you are sexist.” "You're either with us, the good ones, or you're one of the bad ones." |
| Appeal to emotion | Using fear or sympathy instead of reasons. It replaces reasons with feelings. | “If you don't buy this insurance, your family could suffer.” “Support this cause because it will make you feel like a good person.” |
| Appeal to the majority (Ad populum) |
Trying to win acceptance of a thesis by appealing to popular feeling, fashion, or tradition. | “Everyone does it, so it's fine.” "You should buy the new phone X. Millions of people are using it, so it must be the best." "If the movie has made so much money and everyone says it is a masterpiece, it can't be bad." |
| Misrepresenting the opponent's position "Straw man" Scarecrow |
Distorting or exaggerating the opponent's argument to make it easier to attack or refute, and then attacking that distorted version instead of the original argument. | Person A: "I think we should invest more in public education." Person B: "So you want us to spend all our money on teachers and books, leaving the army and the police without funds. Irresponsible!" Person A: "I would like the company to offer more flexible schedules." Person B: "They want people to come to work whenever they feel like it and ruin productivity." The politician proposes: "It is necessary to reduce polluting emissions from factories." The opponent criticizes: "The politician wants to end all industry and leave us without jobs." |
Classic books to go deeper (in Spanish or with translation)
- “Lógica informal” – Douglas Walton (very complete, university level).
- “Las falacias” – Carlos Ruiz Schneider.
- “Cómo ganar una discusión” – Diego Ruiz.
- “El arte de tener razón” – Arthur Schopenhauer (classic on stratagems, though not strictly informal logic).
- “Pensar bien, sentirse bien” – Walter Riso (more popular/divulgative).
- “Las trampas del razonamiento” – Madsen Pirie.
To comment on or discuss this article
Click the link to access the discussions on the different networks
Next related page
Categories: Home -> Philosophy
Last updated: 2025-10-29
| | | |
This site was written based on publicly available free articles from the internet.
The content of this site is available under the: Creative Commons Attribution 4.0 International (CC BY 4.0) license.
You can freely copy, redistribute and modify the material, as long as the source is mentioned: liberwiki.com