Logical fallacies adopted from steve richardson george mason university
This presentation is the property of its rightful owner.
Sponsored Links
1 / 17

Logical Fallacies (Adopted from Steve Richardson, George Mason University) PowerPoint PPT Presentation


  • 37 Views
  • Uploaded on
  • Presentation posted in: General

Logical Fallacies (Adopted from Steve Richardson, George Mason University). Zainal A. Hasibuan/Siti Aminah Fakultas Ilmu Komputer Universitas Indonesia. Definitions. Logic is the set of rules by which one can formulate convincing arguments It is "the science of argument."

Download Presentation

Logical Fallacies (Adopted from Steve Richardson, George Mason University)

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Logical fallacies adopted from steve richardson george mason university

Logical Fallacies(Adopted from Steve Richardson, George Mason University)

Zainal A. Hasibuan/Siti Aminah

Fakultas Ilmu Komputer

Universitas Indonesia


Definitions

Definitions

  • Logic is the set of rules by which one can formulate convincing arguments

  • It is "the science of argument."

  • When presenting an argument, one takes a set of premises that are proven to be true, and uses logic to show how they prove a certain "foregone conclusion."

  • Logical errors in scientific writingsare known as fallacies


Logical errors in scientific writings

Logical errors in scientific writings

  • If an argument contains a fallacy, then the conclusion will not necessarily be proven

  • Some fallacies are just accidental, but they can also be used to trap an unwary listener or reader into believing faulty conclusions


Three general categories of logical fallacies

Three general categories of logical fallacies

  • Material fallacies

    • Deal principally with a premise and its evidence.

    • When the premises of an argument, or its evidence, contain material fallacies, the conclusion is not sufficiently proven.

    • "Material fallacies arise out of the fabric (or 'material') used to express an argument."

  • Fallacies of relevance

    • Deal principally with the relationship between the premise/evidence, and the conclusion of the argument.

    • For example, someone who tries to prove a point using emotion, or who proves the wrong point, commits a fallacy of relevance.

    • The point that is proved is usually "an issue about which people have strong opinions, so that no one notices how their attention is being diverted" from the real issue.

  • Verbal fallacies.

    • Deal principally with the misusage of words.

    • An argument which contains "improper or ambiguous use of words" is invalid.


Material fallacies

Material Fallacies

  • False Cause

    • Assuming that one event is caused by another, just because one happens after the other, is the fallacy of false cause. The two events could have both been caused by another event, or they could be totally unrelated.

    • For example: "More people die in hospitals than anywhere else. Therefore, going to a hospital causes death

  • Hasty Generalization

    • A hasty generalization is a general rule that is formed from only a few examples, or examples that are really exceptions.

    • For example: "A bear lives at the zoo, therefore, all bears live at zoos.“

  • Misapplied Generalization

    • Generalizations applied to cases that are exceptions to the rule are said to be misapplied.

    • For example: "Tools are useful, therefore this hammer will be useful." One may not need a hammer, or the hammer may be broken.


Material fallacies1

Material Fallacies

  • False Dilemma

    • When an argument overlooks alternative possibilities, it creates a false dilemma.

    • For example: "America: Love it or Leave it."

  • Compound Question

    • A compound question is one which is phrased in such a way so as to unfairly limit the possibilities of one's answer.

    • For example: "Are you still as selfish as you used to be?" Even if one answers "no," one would still be admitting that one had been selfish in the past.

    • One subset of the compound question fallacy is the persuasive definition.

    • Redefining the terms of an argument to make them support the conclusion is the persuasive definition fallacy.

  • False Analogy

    • When an analogy is drawn between dissimilar objects or ideas, it is called a false analogy.

    • Comparing "apples and oranges" is a well known example of a false analogy.


Material fallacies2

Material Fallacies

  • Contradictory Premises

    • A conclusion which is drawn from premises which cannot both be true at the same time is the fallacy of contradictory premises.

    • For example: "'What would happen if an irresistible force met an immovable object?' (One student's answer: 'An inconceivable smash!')"

  • Circular Reasoning

    • An argument which contains the fallacy of circular reasoning uses its conclusion as support of its premises.

    • It uses "the original thesis as proof of itself."

    • For example: "C. S. Lewis was a good author, because he wrote good books. I know he wrote good books because he was a good author."


Material fallacies3

Material Fallacies

  • Insufficient or Suppressed Evidence

    • Someone who uses the fallacy of insufficient evidence draws a conclusion from only a few unrepresentative examples.

    • For example: "That type of car is poorly made; a friend of mine has one, and it continually gives him trouble."

    • An argument that uses the fallacy of suppressed evidence uses as evidence only the facts that support the conclusion, disregarding the rest of the pertinent facts.

    • This fallacy illustrates how the conclusion was formed before all the evidence for it was gathered, or even in spite of it.

    • In scientific writing, this fallacy is seen in "a failure to look for evidence that will confirm or deny a proposed hypothesis," and it is also seen "when one believes an alternate explanation refutes another explanation without a comparison of the merits between the two explanations."


Fallacies of relevance

Fallacies of Relevance

  • Fallacies of relevance deal principally with the relationship between the premise/evidence, and the conclusion of the argument.

  • For example, someone who tries to prove a point using emotion, or who proves the wrong point, commits a fallacy of relevance.

  • The point that is proved is usually "an issue about which people have strong opinions, so that no one notices how their attention is being diverted" from the real issue.


Fallacies of relevance1

Fallacies of Relevance

  • Irrelevance

    • An argument is irrelevant if it proves or disproves the wrong point.

    • This fallacy is really a broad category that includes almost all of the fallacies of relevance.

    • "In a discussion of the relative safety of different makes of car, for instance, the issue of which cars are made domestically and which are imported is a red herring.“

  • Personal Ridicule

    • Someone who ridicules his opponent instead of addressing the premises of the argument commits this fallacy.

    • "You wouldn't believe someone with his political views would you?"

    • One type of the personal ridicule fallacy is the 'straw man.' When someone uses this fallacy, he applies a characterization or stereotype to his opponents to make them easy to refute.

    • For example, saying that "a person who advocates reduced military spending is . . . in favor of giving in to the Russians," is a straw man fallacy.


Fallacies of relevance2

Fallacies of Relevance

  • Appeal to the People

    • Using the feelings, actions, and/or prejudices of the general populous as a support of an argument may invalidate it.

    • "Everyone's doing it!"

  • Appeal to Authority

    • Using the opinion of an expert in a field other than the one being discussed may invalidate the argument.

    • "Coke is the favorite soda of 9 out of 10 actors, therefore we should have Coke at our picnic."

  • Appeal to Ignorance

    • Assuming that a premise is correct because it can't be disproved displays the fallacy of ignorance. This is the "guilty until proven innocent" fallacy.

    • "A classic example is this statement by Senator Joseph McCarthy, when asked to back up his accusation that a certain person was a communist: 'I do not have much information on this except the general statement of the agency that there is nothing in the files to disprove his Communist connections."


Fallacies of relevance3

Fallacies of Relevance

  • Appeal to Pity

    • An argument that uses this fallacy may be invalid because it depends on the idea that one will be more likely to accept the conclusion if one feels sorry for someone or something associated with it. This is the "victim" mentality.

    • "I know I flunked every exam, but if I don't pass this course, I'll have to retake it in summer school. You have to let me pass!”

  • Appeal to Force

    • Threats and intimidations used to force someone to accept an argument constitute an appeal to force.

    • "If you don't do what I tell you, you'll lose your job!"

  • Appeal to Money

    • Advertisers frequently appeal to the desire to save money or get more money to induce people to make purchases. Despite their success, their appeals are fallacious.

    • "Buy our products and save up to $50 every year!"


Fallacies of relevance4

Fallacies of Relevance

  • Emotive Language

    • Using a word, phrase, or argument only to stimulate emotions invalidates ones argument.

    • "President Clinton's best allies are the Clinton Haters." The author of this quote used the term "Clinton Haters" to stimulate emotions. He described the "Clinton Haters" as willing to "say anything and charge him [Clinton] with anything that comes out of their heads when they get out of bed in the morning." He gives no evidence that anyone that impulsive actually exists. In this case, this fallacy is similar to the personal ridicule fallacy.

  • Tu Quoque

    • This fallacy is used as a defense, where the person being criticized accuses his critic of doing the same thing himself. ("Tu quoque" means "you too.")

    • "Son, it is your bedtime. Go to bed." "But dad, you are staying up!"

  • Genetic Error

    • When someone disregards a premise or an argument only because of where it came from, they commit a genetic error. "The source of an argument is irrelevant so far as logical proof is concerned.“

    • "[Clinton's] lieutenants . . . dismiss even legitimate questions as products of 'the attack machine.'"


Fallacies of relevance5

Fallacies of Relevance

  • Anthropomorphism

    • When someone projects human feelings and qualities to animals and inanimate objects, he commits a fallacy of anthropomorphism.

    • "After millions of years of work, Nature had created many diverse species of plants and animals."

  • Non Sequitur

    • When the premises of an argument are not logically connected to the conclusions, the argument contains a non sequitur.

    • "Trees are green; therefore human beings enjoy spinach."


Verbal fallacies

Verbal Fallacies

  • Verbal fallacies deal principally with the misusage of words. An argument which contains "improper or ambiguous use of words" is invalid. Here are some descriptions and examples of verbal fallacies.

  • Ambiguity

    • Using undefined words or words whose meaning is vague constitutes an ambiguity. For example, in 1997 the Commonwealth of Virginia proposed buying "probe kits" for every student to help in math. Regarding this ambiguity, C. R. Taft said,

    • "To be sure, there is the matter of 6,000 'probe kits,' or data-collection devices. What data these devices collect and how they do so was never defined clearly."

  • Equivocation

    • Someone who uses a word in more than one sense, but gives the impression that only one meaning was meant, is using an equivocation. Anyone who presents an argument needs to use only one definition for each of his terms. When more than one definition is used for a certain word, it can cause confusion and be misleading.

    • "Death is a subject of utmost gravity. Gravity is what keeps us from falling off the Earth. Thus, death is primarily what keeps us from falling off the Earth."


Verbal fallacies1

Verbal Fallacies

  • Composition

    • Assuming that a group will have the same qualities as the individuals in it is the fallacy of composition. This fallacy and the next one are types of equivocation. "In the fallacy of composition, the individual terms that comprise a group . . . are equivocally confused with the collective term."

    • "A spider is a beneficial member of an ecosystem. Therefore, introducing millions of spiders into an ecosystem would be advantageous."

  • Division

    • When one assumes that the individuals in a group will have the same qualities as the group they are in, one commits the fallacy of division.

    • "That orchestra is the best in the world, therefore it is made up of the best musicians in the world." However, the best orchestra in the world may not have the world's best solo violinist.

  • Amphibology

    • A sentence that is structured in such a way as to make more than one interpretation possible is an amphibology.

    • "Wanted to sell: A highchair for a baby with a broken leg."


Verbal fallacies2

Verbal Fallacies

  • Abstraction

    • Taking a quote out of context is known as abstraction. Using this fallacy can totally change what was originally meant. Francis Bacon purportedly said,

    • "Philosophy inclineth a man's mind to atheism." But what he actually said was, "A little philosophy inclineth man's mind to atheism, but depth in philosophy bringeth men's minds about to religion."

  • Identifying logical fallacies is an important skill for everyone to have.

  • It not only helps one to avoid accepting false conclusions, but it also helps one to learn better reasoning and debating skills.

  • The process of looking for logical fallacies can help one to better understand the subject one is reading about or discussing.

  • Knowing how to identify fallacies and how to avoid using them, can make one better prepared to refute false ideas and present the truth.


  • Login