Escher's "Day and Night"
A logical fallacy is a false argument that
depends on emotional manipulation, contorted logic, or leaps of faith. Sound
argumentation depends on valid logic, empirical facts, and coherent reasoning. Actually,
despite that definition, it turns out that logical fallacies can be effective
argumentative tools. When in the hands of clever arguers, these logical fallacies may end
up convincing unsuspecting listeners or readers that a shallow or weak argument is valid.
Still, it is a good idea to
recognize
and avoid logical fallacies in arguments because, once discovered,
these fallacies destroy both your argument and your credibility. This suggestion does not
mean that you must exclude all appeals to emotion, but rather
that you should be
cautious: know how to make arguments that are grounded logically, and then pose them with
the passion that makes you convinced of the truth in the first place.
Below are some of the most common logical fallacies you will likely encounter in arguments--both yours and the arguments of others:
1. False Analogy
Assuming that because one thing resembles another, conclusions drawn from one apply to the other.
2. Post hoc, ergo propter hoc (False cause)
Assuming that because one thing preceded another, the former caused the latter.
3. False Dilemma (Either-or reasoning)
Assuming that there are only two possible solutions to a problem, and yours is the correct one.
4. Begging the question (Circular reasoning)
Arguing that a claim is true by repeating the claim in different words.
5. Jumping to conclusions (Hasty generalization)
Offering only weak or limited evidence to support a conclusion.
6. Slippery Slope
Pretending that one thing inevitably leads to another.
7. Argumentum ad populum (Bandwagon effect)
Arguing that since most people take a position, the position is therefore true.
8. Argumentum ad hominem (Personal attack)
Demeaning the proponents of a claim instead of refuting their argument.
9. Straw man
Directing the argument against a claim that everyone agrees is weak.
10. Appeal to pity (Sob story)
Manipulating readers' emotions in order to lead them to draw unjustifiable conclusions.
11. Appeal to tradition
Asking readers to
accept the status quo for its own sake.
12. Red herring
Attempting to mislead readers by introducing an irrelevant point or issue.
13. Non sequitur (Logic that does not follow)
Logic that does not follow.
I have built some additional examples to
see how well you understand these dozen fallacies. One last small set of
examples was found side-by-side in the letters
to the editor section of the Star Tribune a little while ago. See if you can
tell which fallacies were committed here.
The web has several online quizzes on fallacies. Check out this one.
For additional discussion and examples of logical fallacies, check out: Prof. Dennis Jerz website at Seton Hill (Pittsburgh, PA)