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CMSD 3070: Website Evaluation for Communication Sciences (Finn): Fallacy Alert!

Fallacy Alert!

Common Fallacies

The Internet Encyclopedia of Philosophy has comprehensive explanations of fallacies of reasoning.


Hasty Generalization:
Making an assumption about a group or range of things based on an inadequate sample:  "My roommates physics class is hard; my physics class is hard; all physics classes are hard."


Post Hoc (AKA 'False Clause')
If B follows A, then A caused B: "In 1998 taxes were raised and violent crime went up. Higher taxes led to an increase in violent crime.


Slippery Slope:
A chain of events must inevitably lead to a single consequence:
"If I don't graduate I won't get a good job and I'll spend my life selling buttons in Woolworth's.


Weak Analogy:
Comparing two or more things that aren't really alike:
"Guns and hammers both kill people. If gun ownership requires a permit, so should hammer ownership.

Appeal to Authority:
Citing an unqualified person, organization or other resource as an authority. 

Ad Hominem:
Attacking the opponent instead of their argument .
(Any political attack ad.)


Ad Populum:
Using popularity as proof of value :
"Tune in to Channel 6 News, the most watched newscast in the state."


Straw Man:
Citing a weak, incorrect version of an opponent's argument, then attacking it.


Red Herring:
Dwelling on a side issue to distract the audience from the main issue.


False Dichotomy:
Creating an either/or argument rather than covering all possible options:
"The house is in terrible shape - either we tear it down or risk the lives of everyone who lives there."


Begging the Question:
Not providing evidence to back up an assertion, or using circular reasoning (premise is the same as conclusion).

"Murder is morally wrong so euthanasia is morally wrong. "


Using more than one definition of a word or phrase:
"Giving money to charity is the right thing to do, so charities have a right to our money ."