Logically Fallacious Resources
Formal fallacies and invalid argument structure
Formal fallacies are mistakes in logical structure. Even if the premises sound plausible, the conclusion does not follow from the form of the argument.
Structure first
A formal fallacy can often be identified by abstracting away the subject matter and looking only at the shape of the argument.
Useful for careful argument analysis
Formal fallacies are especially important when evaluating deductive arguments, syllogisms, conditionals, and claims that present themselves as strict logic.
Related fallacies
See all fallaciesFalse Conversion
The formal fallacy where the subject and the predicate terms of the proposition are switched (conversion) in the conclusion, in a proposition that uses “all” in its premise (type “A” forms), or “some/not” (type “O” forms).
Affirming the Consequent
An error in formal logic where if the consequent is said to be true, the antecedent is said to be true, as a result.
Denying the Antecedent
It is a fallacy in formal logic where in a standard if/then premise, the antecedent (what comes after the “if”) is made not true, then it is concluded that the consequent (what comes after the “then”) is not true.
Illicit Major
Any form of a categorical syllogism in which the major term is distributed in the conclusion, but not in the major premise.
Illicit Minor
Any form of a categorical syllogism in which the minor term is distributed in the conclusion, but not in the minor premise.