The term "logical fallacy" refers to the concept of making an error in terms of reasoning. It is crucial to understand logical fallacies so that they can be identified and avoided when attempting to persuade.
Types of Logical Fallacy
There are many different types of logical fallacy including:
- Formal Fallacy – These are also called deductive fallacies. In deductive fallacy arguments, all premises must be accurate and impossible to be proven otherwise. When this is the case, there is no way that the conclusion can be false.
Example of a valid argument: (1) All dogs have legs. (2) Tiny is a dog. Therefore: (3) Tiny has legs.
- Informal Fallacy – This is an inductive argument.
Example of a strong inductive argument: (1) The sun has not exploded for all its existence. Therefore: (2) The sun will not explode tomorrow.
- Logical and Factual Errors – Any argument in which premises or inferences are poor will result in a fallacious conclusion.
Fallacies can also be categorized more specifically based on the cause of the fallacy such as relevance, ambiguity or presumption.
Fallacies of Relevance
Some logical fallacies are caused by assuming that all parts are equally important and, since some parts are important and true, all parts must be important and true.
- Ad Hominem (Personal Attack)
- Bandwagon Fallacy (Argument only appealing because of growing popularity)
- Fallacist’s Fallacy (Rejecting idea's correctness altogether because of a fallacy)
- Fallacy of Composition (Regarding whole and property)
- Fallacy of Division (Relating whole to part and part to whole)
- Gambler’s Fallacy (Regarding short term deviations and probability)
- Genetic Fallacy (Acceptance or rejection of concepts based on source as opposed to merit)
- Irrelevant Appeals (Attempt to persuade with irrelevant information)
- Moralistic Fallacy (Fallacy of assumption that the world is as it should be)
- Naturalistic Fallacy (Fallacy regarding how the world is)
- Red Herring (Uses irrelevant information or other techniques to distract from the argument)
- Weak Analogy (Analogies that are not strongly linked)
Fallacies of Ambiguity
A logical fallacy can be caused by a lack of clarity or by a misunderstanding of the words.
- Accent Fallacies (Based on stress of word or word parts)
- Equivocation Fallacy (Words are used multiple times with different meanings)
- Straw Man Fallacy (Misrepresentation in order to make argument look weak)
Fallacies of Presumption
Presumption of truth without proof can cause a logical fallacy.
- Affirming the Consequent (Poorly formed argument without reasonable premise)
- Arguing from Ignorance (Inference of truth to argument just because it is not known to be false)
- Begging the Question / Circular Reasoning (Conclusion is among the premises)
- Complex Question Fallacy (Involves questionable assumption)
- Cum Hoc Fallacy (Poorly assumed correlation of two things)
- False Dilemma / Bifurcation Fallacy (Requiring a choice between only two choices when another is available)
- Hasty Generalisation Fallacy (Uses only one, abnormal situation)
- "No True Scotsman" Fallacy (Reinterpretation of evidence)
- Post Hoc Fallacy (Assumption of cause and effect)
- Slippery Slope Fallacy (False assumption of consequences of action)
- Sweeping Generalisation Fallacy (Too broad of an application of a premise)
- Subjectivist Fallacy (Lack of questioning of premises)
- Tu Quoque Fallacy (The concept of “someone else did it so I can”)
By considering these different types of logic errors and logical fallacy, it is easier to spot these errors when they occur and to avoid making these errors in logic yourself.