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Dr. Jay
VerLinden
Communication
Department
College of Arts, Humanities
and Social Sciences
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Argumentation and Critical Thinking Tutorial

INFORMAL FALLACY DEFINITIONS
GROUP 2: FALLACIES BASED ON FORMS OF REASONING

 

Quick Review

This page reviews the definitions of seventeen fallacies. A common English name for each fallacy is used, with alternative names in parentheses. This page does not describe the fallacies in detail, so you should be sure to read some material on these fallacies before you take the tests.

These fallacies have been grouped together because they can all be considered to be based on forms of reasoning. Keep in mind that they could also be grouped in other ways, as could the fallacies in other sections of this site.

AD ANTIQUITATEM : a specific type of false sign that reasons something is necessarily better because it is old or worse because it is new.

AD CRUMENAM : a specific type of false sign that reasons there is necessarily a direct relationship between cost and quality, thus concluding that something is necessarily of higher quality because it costs more or lower quality because it costs less, or that someone is necessarily a better person because he or she is wealthy or highly paid or a worse person because he or she is poor.

AD LAZARUM: a specific type of false sign that reasons there is necessarily an inverse relationship between cost and quality, thus concluding that something is necessarily a better value because it costs less, or that someone is necessarily a better person because he or she is poor or a worse person because he or she is wealthy.

AD NOVITATEM : a specific type of false sign that reasons something is necessarily better because it is new or worse because it is old.

ANECDOTAL EVIDENCE: a particular type of hasty generalization, in which individual stories are substituted for a larger sample when supporting a generalization.

COMPLEX CAUSE: a specific type of false cause that involves mistakenly attributing the cause of an event to a simple cause when the cause is more complex.

COMPOSITION: arguing that what is true of an individual part of an object must be true of the entire object.

CONCOMITANT VARIATION (joint variation, joint effect, cum hoc ergo prompter hoc ): a particular type of false cause fallacy that argues since two events happened at the same time one event caused the other.

DIVISION: arguing that what is true of an entire object must also be true of every individual part of that object.

FALSE ANALOGY (questionable analogy, wrongful comparison, imperfect analogy): drawing a conclusion based on an analogy when the items being compared are not similar enough to sustain the analogy.

FALSE CAUSE (questionable cause): arguing that one event caused another without sufficient evidence of a causal relationship.

FALSE CRITERIA (questionable criteria): reasoning that applies irrelevant criteria to the subject of the argument.

FALSE SIGN (questionable sign): drawing a conclusion based on sign reasoning when there is not really a direct relationship between the alleged sign and the subject of the conclusion.

HASTY CONCLUSION (jumping to a conclusion): drawing a conclusion without enough evidence to support that conclusion.

HASTY GENERALIZATION (over generalization, converse accident, secundum quid ): Arguing that what is true of a few members of a class is true of all members of the class.

NATURAL LAW FALLACY: a specific type of false analogy that reasons what is true about nature must be true about humans.

POST HOC (post hoc ergo prompter hoc ): a specific kind of false cause fallacy arguing that because one event preceded another event the first even must have caused the second event.

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