Informal FallacyTaxonomy: Logical Fallacy > Informal Fallacy
Accident, Ambiguity, Appeal to Ignorance, Begging the Question, Black-or-White Fallacy, Composition, Division, Non Causa Pro Causa, One-Sidedness, Overgeneralization, Red Herring Fallacy, Special Pleading, Vagueness, Weak Analogy
The distinction between formal and informal fallacy is based on the distinction between form and content, specifically, between the logical form of an argument and its non-logical content. A formal fallacy is a type of argument that is fallacious solely on the basis of its logical form. In contrast, an informal fallacy is, of course, one that is not formal, that is, what makes such an argument fallacious is not purely a matter of logical form.
In addition to non-logical content, the context of an argument is also not a part of its logical form and plays a role in the fallaciousness of many of the informal fallacies. By "context", I refer to the linguistic or social setting of an argument; for instance, a particular argument may occur in the context of a debate. See the Exposure section, below, for specifics and examples.
Frequently, but not exclusively, informal fallacies occur in non-deductive reasoning, which relies on content as well as form for cogency. Also, because content is important in informal fallacies, there are cogent arguments with the form of the fallacy. For this reason, when forms are given in the entries for individual informal fallacies, this is for identification purposes only―that is, one cannot tell from the form alone that an instance is fallacious, since content is also relevant. Rather, the forms will help to differentiate between distinct types of informal fallacy.
As a logical fallacy, Informal Fallacy is the most general fallacy committed by arguments that are fallacious for informal reasons. However, a given fallacious argument would be classified as an Informal Fallacy only if it could not be given a more specific classification. For this reason, there is no Example of Informal Fallacy given; instead, see the Examples under the Subfallacies, above.
Since an informal fallacy is a type of argument whose content or context is relevant to its fallaciousness, logical fallacies can be informal for the following reasons, among others:
- Linguistic: "Linguistic" refers, of course, to language, and a linguistic fallacy is one in which some feature of the non-logical language in which an argument is expressed plays an essential role. For instance, words and phrases are often ambiguous, that is, they have more than one possible meaning. As a result, arguments as a whole may admit more than one interpretation. When the ambiguity of an argument plays an essential role in making a formally invalid argument appear to be valid, it commits a linguistic fallacy.
- Dialectical: "Dialectic" refers to reasoning that occurs in a dialogue or debate between two or more people. So, a "dialectical" fallacy is one in which dialogue plays an essential role. The most prominent such fallacy is the straw man fallacy: In a straw man argument, the arguer misrepresents the argument or claim of another participant in the dialogue. Thus, straw man arguments can only occur within the context of such a debate.
Example: The Straw Man Fallacy
- Epistemological: "Epistemology" is the philosophical study of knowledge, so that an "epistemological" fallacy is one in which the nature of knowledge plays an essential role. For instance, circular arguments are technically valid―that is, if their premisses are true then their conclusions must also be true. However, as should be obvious, circular reasoning cannot advance knowledge, since it ends up in the same place it started. Thus, circular reasoning commits an epistemological fallacy.
Example: Begging the Question
S. Morris Engel, With Good Reason: An Introduction to Informal Fallacies (Fifth Edition) (St. Martin's, 1994). A good textbook for beginners.
- T. Edward Damer, Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments (Third Edition) (1995). Another introductory textbook on informal fallacies, but more advanced than Engel. It covers more fallacies than Engel but in a drier style.
- S. Morris Engel, Fallacies and Pitfalls of Language: The Language Trap (1994). This book covers the same ground as Engel's textbook, above, but in a popular, non-textbook style.
- Douglas N. Walton, Informal Fallacies (1987). This is not a textbook, but a monograph by one of the most prominent scholars of informal fallacies. A more advanced treatment than Engel or Damer.