Logical Fallacies

The first author came up with the original idea, based on William Safire's collection of grammatical rules in a similar format. The second author contributed many (perhaps most) of the examples. Responsiblity for choosing the best ones rests exclusively with the first author.

• Ad hominem arguments are the tools of scoundrels and blackguards. Therefore, they are invalid.
• If you had any consideration for my feelings, you wouldn't argue from an appeal to pity.
• What would your mother say if you argued from an appeal to sentiment?
• I don't understand how anyone could argue from an appeal to incredulity.
• If you argue from an appeal to force, I'll have to beat you up.
• You are far too intelligent to accept an argument based on an appeal to vanity.
• Everyone knows that an argument from appeal to popular opinion is invalid.
• Circular reasoning means assuming what you're trying to prove. This form of argument is invalid becuase it's circular.
• As Aristotle said, arguments from an appeal to authority are invalid.
• Post hoc ergo proptor hoc arguments often precede false conclusions. Hence, this type of argument is invalid.
• Using the Argumentum ad Consequentiam makes for unpleasant discussions. Hence, it must be a logical fallacy.
• The argumentum ad nauseum is invalid. The argumentum ad nauseum is invalid. The argumentum ad nauseum is invalid. If three repetitions of this principle haven't convinced you, I'll just have to say it again: the argumentun ad nauseum is invalid.
• Ancient wisdom teaches that the argumentum ad antiquitatem is invalid.
• An argument is emotional and no substitute for reasoned discussion. But proof by equivocation is a kind of argument. Thus, a proof by equivocation is no substitute for a valid proof.
• If we accept slippery slope arguments, we may have to accept other forms of weak arguments. Eventually, we won't be able to reason at all. Hence, we must reject slippery slope arguments as invalid.
• A real logician would never make an argument based on the "No true Scotsman" fallacy. If anyone who claims to be logical and makes arguments based on this fallacy, you may rest assured that s/he is not a real logician.
• An argument based on a logical fallacy often leads to a false conclusion. Affirming the consequent often leads to a false conclusion. Therefore, affirming the consequent is a fallacy.

The following additional fallacies were sent in by Rev. Hugh Ryunyo King:

• The fallacy of the undistributed middle is often used by politicians, and they often try to mislead people, so undistributed middles are obviously misleading.
• Reasoning by analogy is like giving a starving man a cookbook.
• Non sequitur is a Latin term, so that's a fallacy too.
• And I bet the gambler's fallacy is also invalid - I seem to be on a roll!

Please feel free to submit other logical fallacies (in never-say-never form) to benham@pegasus.montclair.edu. I will try to incorporate the best ones into this page, even at the expense of replacing some of the ones above.

Last modified: December 18, 2002