Have A Fallacy-Free Day!

As a university professor (I also served as an administrator), a few short years ago, I taught an introductory course in philosophy. My class was usually comprised of shell-shocked freshmen, disinterested sophomores and seniors who needed the class to graduate (with a couple of middle-aged students sprinkled in). It was usually my practice in the second week to address the subject of fallacies. Fallacies are a mistake in reasoning; an argument that fails to provide adequate logical support for the truth of its conclusion yet appears convincing or persuasive in some other way. Common examples include both formal fallacies (structural errors in deductive logic) and informal fallacies (efforts to persuade by non-rational appeals). It was always interesting to see how many of my students, up to the point where they had become students of mine, had nurtured the habit of basing their arguments and beliefs, to varying degrees, on fallacies. Below I have outlined a number of informal fallacies, see if any look familiar to you:

appeal to ignorance ( argumentum ad ignoratiam )

The informal fallacy of supposing that a proposition must be true because there is no proof that it is false .

Example: "The F.B.I. investigation was never able to establish that Smith was not at the scene of the crime on the night of June 25th, so we may safely conclude that he was there."

appeal to authority ( argumentum ad verecundiam )

The informal fallacy of claiming that we ought to accept the truth of a proposition because of some personal feature of the individual who affirms it.

Example: "The former Governor believes that aliens have landed in the Arizona desert, so aliens must have landed in the Arizona desert."

ad hominem argument (argument against the person)

The informal fallacy of supposing that a proposition should be denied because of some disqualifying feature of the person who affirms it. This fallacy is the mirror image of the appeal to authority . In its abusive form, ad hominem is a direct (and often inflammatory) attack on the appearance, character, or personality of the individual.

Example: "Jeremy claims that Susan was at the party, but since Jeremy is the kind of person who has to ride to work on the city bus, it must be false that she was there."

A circumstantial ad hominem accuses the person of having an alternative motive for defending the proposition or points out its inconsistency with the person's other views. Tu quoque (the "so do you" fallacy) uses a similar method in response to criticism of a position already held.

appeal to emotion ( argumentum ad populum )

The informal fallacy of persuading someone to accept (or reject) a conclusion by arousing favorable (or unfavorable) emotions toward it or by emphasizing its widespread acceptance (or rejection) by others.

Example: "Nobody with an ounce of common sense or a single shred of integrity believes that our President is truly an effective leader. Therefore, the President is not an effective leader."

appeal to force ( argumentum ad baculum )

The informal fallacy of securing agreement by threatening adverse consequences in case of disagreement.

Example: "Anyone who believes that the government has exceeded its proper authority under the constitution will be subjected to severe harassment by the provincial police. Therefore, the government has not exceeded its authority."

irrelevant conclusion ( ignoratio elenchi )

Reasoning that misses the point. The informal fallacy of defending the truth of a proposition by appeal to an argument that is actually concerned with something else .

Example: "Parents with large incomes can buy lots of things for their children. Therefore, the children of wealthy parents are happy."

fallacy of accident {Lat. a dicto simpliciter ad dictum secundum quid }

The informal fallacy of applying a generally reliable rule to a particular case without considering the qualifying features that might make it an exception to the rule.

Example: "Since authors of best-selling books usually appear on television talk shows, and the Pope is in fact the author of a best-selling book, it follows that the Pope must soon appear on a television talk show."

converse accident {Lat. a dicto secundum quid ad dictum simpliciter }

The informal fallacy of using exceptional specific cases as the basis for a general rule, omitting reference to their qualifying features.

Example: "It rained on my birthday this year and it rained on my birthday last year. Therefore, it always rains on my birthday."

false cause

The informal fallacy of affirming the presence of a causal relationship on anything less than adequate grounds . Post hoc, ergo propter hoc is a common variety of this fallacy.

Example: "After drinking milk for twenty years, Melanie became addicted to cocaine. Therefore, drinking milk caused her cocaine addiction."

begging the question ( petitio principii )

Circular reasoning. The " informal fallacy " of (explicitly or implicitly) assuming the truth of the conclusion of an argument as one of the premises employed in an effort to demonstrate its truth.

Example: "Since firefighters must be strong men willing to face danger every day, it follows that no woman can be a firefighter."

complex question

The informal fallacy of framing an issue as if it involved genuine alternatives while implicitly assuming the truth of the desired conclusion.

Example: "Do you expect Peter to speak for thirty minutes or fifty? In either case, you acknowledge that he will be long-winded."

equivocation

The informal fallacy that can result when an ambiguous word or phrase is used in different senses within a single argument.

Example: "Odd things arouse human suspicion. But seventeen is an odd number. Therefore, seventeen arouses human suspicion."

amphiboly

The informal fallacy that can result when a sentence is ambiguous because of its grammatical structure , even if all of its terms are clear.

Example: "One morning in Africa, Captain Spaulding shot an elephant in his pajamas. Therefore, it is dangerous for large animals to wear human clothing."

fallacy of accent

An informal fallacy that arises from the ambiguity produced by a shift of emphasis in spoken or written language.

Example: "Joan said that she never wants to see another alien invasion movie, so we won't show her another one; we'll just play this same one over and over again."

fallacy of composition

The informal fallacy of attributing some feature of the members of a collection to the collection itself, or reasoning from part to whole .

Example: "Each of the elements in this compound (NaCl) is poisonous to human beings; therefore, this compound is itself poisonous to human beings."

fallacy of division

The informal fallacy of attributing some feature of a collection to the members of that collection individually, or reasoning from whole to part .

Example: "Today's newspaper has a lot of grocery ads, so each page of today's newspaper has a lot of grocery ads."

Today, see how many times you hear (or overhear) or read, where an individual, organization or news program (and yes, newspapers if you still read them) indulges in any of these informal fallacies. Some of these fallacies are so farfetched, that maybe they won't come up in anything you hear or read throughout the course of the day. While others, are far too common, in my opinion, to miss (especially in our current political discourse). I've made the examples of the above-mentioned informal fallacies pretty blatant and obvious. Those that you may encounter, are bound to be a little more discreet. Thank you for indulging my professorial streak and like the title says: have a fallacy-free day!