Logical Fallacies

This page contains Links and Quotes.

Web-pages about Logical Fallacies:

Stephen's Guide to the Logical Fallacies, by Stephen Downes, in two formats, brief summaries plus page-links & almost all in one page. (but it's missing the final three fallacy-categories)

and Jon Shemitz has brief definitions for Common Argument-Fallacies.

The Writing Center at the University of North Carolina explains Arguments and Fallacies and gives "tips on avoiding these fallacies."

Glen Whitman (Cal-State Northridge) shares Rhetorical Strategies (offensive and defensive) for using fallacy-knowledge during formal competitive debates.  (of course, these tricks can also be used during informal debates, and for political persuasion, advertising,...)

Dean & Laura VanDruff share some Conversational Tricks and Fallacies.

Robert Harris offers a logical analysis of Material Fallacies (Parts 1-2-3).

Craig Rusbult (editor of this page) describes Circular Reasoning (including "a superficial similarity... and important difference... between scientific logic and circular logic") and Strawman Arguments which "are intellectually dishonest" because they "pretend that something false is true."

Logic is worldview-independent, as you can see in pages about fallacies by Nathaniel & Hans Bluedorn (Christian Logic) and Mathew (infidels.org).

Here are more high-quality resources:  42 Fallacies: Deductive & Inductive (Michael Labossiere) — The Fallacy Files (Gary Curtis) — Fallacies and Causal Logic (from Allyn & Bacon) — An Encyclopedia of Logical FallaciesLogical Fallacies in Psychology (Kenneth Pope)

Quotations about Logical Fallacies

Quoting from the pages linked-to above:

A fallacy is an error in an argument that makes the argument unacceptable. ...  Pay attention — scrutinize and analyze the arguments presented to you.   (Robert Harris)

We've all probably fallen for them — and perhaps used them — from time to time.   (Kenneth Pope)

A fallacy is, very generally, an error in reasoning.  This differs from a factual error, which is simply being wrong about the facts.  To be more specific, a fallacy is an "argument" in which the premises given for the conclusion do not provide the needed degree of support.   (Michael Labossiere)

However, not just any type of mistake in reasoning counts as a logical fallacy.  To be a fallacy, a type of reasoning must be potentially deceptive, it must be likely to fool at least some of the people some of the time.  Moreover, in order for a fallacy to be worth identifying and naming, it must be a common type of logical error. ...  In logical self-defense, you need to be able to spot poor reasoning, and — more importantly — to understand it.  To be able to correct others' mistakes, or to refute them convincingly, you need to understand why they are wrong.   (Gary Curtis)

It is particularly easy to slip up and commit a fallacy when you have strong feelings about your topic — if a conclusion seems obvious to you, you're more likely to just assume that it is true and to be careless with your evidence. ...  It is important to realize two things about fallacies:  First, fallacious arguments are very, very common and can be quite persuasive, at least to the causal reader or listener.  You can find dozens of examples of fallacious reasoning in newspapers, advertisements, and other sources.  Second, it is sometimes hard to evaluate whether an argument is fallacious.  An argument might be very weak, somewhat weak, somewhat strong, or very strong.  An argument that has several stages or parts might have some strong sections and some weak ones.   (Writing Center at University of North Carolina)

When arguing a case or examining the arguments of another, look for these common fallacies.  Avoiding these problems makes a case stronger.  Further, finding these fallacies in other's statements can make your rebuttal easier.   (Jon Shemitz) [italics added]

This is a guide to using logical fallacies in debate.  And when I say "using," I don't mean just pointing them out when opposing debaters commit them — I mean deliberately committing them oneself, or finding ways to transform fallacious arguments into perfectly good ones.  ...  If you think a fallacious argument can slide by and persuade... you're going to make it, right?  The trick is not getting caught.   (Glen Whitman) [italics added]

Fallacious reasoning keeps us from knowing the truth, and the inability to think critically makes us vulnerable to manipulation by those skilled in the art of rhetoric.   (Encyclopedia of Logical Fallacies)

Informal fallacies are instances of murky reasoning that can cloud an argument and lead to unsound conclusions.  Because they can crop up unintentionally in anyone's writing, and because advertisers and hucksters often use them intentionally to deceive, it is a good idea to learn to recognize the more common fallacies.   (Allyn & Bacon)

Stephen Downes describes different types of common fallacies:
    Fallacies of Distraction:  Each of these fallacies is characterized by the illegitimate use of a logical operator in order to distract the reader from the apparent falsity of a certain proposition.
    Appeals to Motives in Place of Support:  The fallacies in this section have in common the practice of appealing to emotions or other psychological factors.  In this way, they do not provide reasons for belief, but merely "trick" people into agreeing with them one way or another without proof.
    Changing the Subject:  The fallacies in this section change the subject by discussing the person making the argument instead of discussing reasons to believe or disbelieve the conclusion.
    Inductive Fallacies:  Inductive reasoning consists of inferring from the properties of a sample to the properties of a whole class of entities. ... All inductive reasoning depends on the similarity of the sample and the population.  The more similar the same is to the population as a whole, the more reliable will be the inductive inference.  On the other hand, if the sample is relevantly dissimilar to the population, then the inductive inference will be unreliable.
    Fallacies Involving Statistical Syllogisms:  A statistical generalization is a statement which is usually true, but not always true. ... Fallacies involving statistical generalizations occur because the generalization is not always true. Thus, when an author treats a statistical generalization as though it were always true, the author commits a fallacy.
    Causal Fallacies:  It is common for arguments to conclude that one thing causes another. But the relation between cause and effect is a complex one. It is easy to make a mistake.
    Missing the Point:  These fallacies have in common a general failure to prove that the conclusion is true.
    Fallacies of Ambiguity:  The fallacies in this section are all cases where a word or phrase is used unclearly.
    Category Errors:  These fallacies occur because the author mistakenly assumes that the whole is nothing more than the sum of its parts.  However, things joined together may have different properties as a whole than any of them do separately.
    Non-Sequitur:  The term non sequitur literally means "it does not follow".  In this section we describe fallacies which occur as a consequence of invalid arguments.
    Syllogistic Fallacies:  ... due to invalid categorical syllogisms.
    Fallacies of Explanation:  ... in attempting to answer the question "why?"
    Fallacies of Definition:  In order to make our words or concepts clear, we use a definition.  The purpose of a definition is to state exactly what a word means.  A good definition should enable a reader to ‘pick out’ instances of the word or concept with no outside help.  For example, suppose we wanted to define the word "apple".  If the definition is successful, then the reader should be able go out into the world and select every apple which exists, and only apples.  If the reader misses some apples, or includes some other items (such as pears), or can't tell whether something is an apple or not, then the definition fails.


this page, assembled by Craig Rusbult, is http://www.asa3.org/ASA/education/think/fallacies.htm