Formal fallacies are errors in the logical structure of an argument. The conclusion does not follow from the premises, regardless of whether the content is true or false.
Example
If A then B.
B, therefore A.
(Affirmation of the consequent.)
Applied example (political)
“If there is prosperity, there is employment. There is employment, therefore there is prosperity.” (Affirming the consequent.)
Applied example (mystical)
“If there is healing, there is faith. There is faith, therefore there is healing.” (The form is invalid.)
Why they matter
- An argument can sound convincing and still be invalid.
- Incorrect form produces unjustified conclusions.
- Detecting them helps automate argument evaluation.
How to spot them
- Analyze the structure (if-then, quantifiers, negations).
- Look for invalid inference patterns.
- Compare with known valid forms.
How to respond
- Point out the invalid structure.
- Suggest a valid alternative form.
- Ask for additional evidence to support the conclusion.