Logical Fallacies

“There’s a mighty big difference

between good, sound reasons

and reasons that sound good.” Burton Hills, cited in Laurence J.

Peter’s Peter, Quotations: Ideas for Our Time (1977), p. 425

What is a logical fallacy?

• A "fallacy" is a mistake,

• and a "logical" fallacy is a mistake in reasoning.

What is a logical fallacy?

• The text Everything’s An Argument clarifies that logical fallacies are not necessarily indicators of flawed logic, but rather are attempts to move and/or manipulate the audience:

“Certain types of argumentative moves are so controversial they have been traditionally classified as fallacies…. But you might find it more interesting to think of them as flashpoints or hotspots because they instantly raise questions about the ethics of argument—that is, whether a particular strategy of argument is fair, accurate, or principled.”

“Fallacies are arguments supposedly flawed by their very nature or structure; as such, you should avoid them in your own writing and challenge them in arguments you hear or read.

That said, it’s important to appreciate that one person’s fallacy may well be another person’s stroke of genius (384–385).”

Fallacies are commonly categorized in these

groups:

• FALLACIES OF RELEVANCE

• FALLACIES OF AMBIGUITY

Fallacies are commonly categorized in these

groups:

• COMPONENT FALLACIES

• FALLACIES OF OMISSION

FALLACIES OF RELEVANCE:

appeal to evidence or examples that are not relevant to the argument at hand.

FALLACIES OF RELEVANCE:

• Appeal to Force (or the "Might-Makes-Right" Fallacy)

• This argument uses threats or some other unpleasant backlash to make the audience accept a conclusion.

FALLACIES OF RELEVANCE:

• Personal Attack (Argumentum Ad Hominem, "Poisoning the Well")

• Attacking or praising the people who make an argument, rather than discussing the argument itself.

FALLACIES OF RELEVANCE:

• Appeal to Authority

• a fallacy when the expert being cited is not really an expert or there are differing opinions among experts.

FALLACIES OF RELEVANCE:

• Appeal to Tradition• This line of thought

asserts that a premise must be true because people have always believed it or done it. Alternatively, it may conclude that the premise has always worked in the past and will thus always work in the future.

FALLACIES OF RELEVANCE:

• Appeal to Improper Authority

• An appeal to a famous person or a source that may not be reliable.

FALLACIES OF RELEVANCE:

• Appeal to Emotion

• Using an appeal to popular assent, often by arousing the feelings and enthusiasm of the multitude rather than building an argument.

FALLACIES OF AMBIGUITY:

These errors occur with ambiguous words or phrases, the meanings of which shift and change in the course of discussion. Such more or less subtle changes can render arguments fallacious.

FALLACIES OF AMBIGUITY

• Equivocation• Using a word in a

different way than the author used it in the original premise, or changing definitions halfway through a discussion.

FALLACIES OF AMBIGUITY

• Equivocation• Example: "Consider

that two wrongs never make a right, but that three lefts do."

FALLACIES OF AMBIGUITY

• Amphiboly • Here, the ambiguity

results from grammatical construction. A statement may be true according to one interpretation of how each word functions in a sentence and false according to another.

FALLACIES OF AMBIGUITY

• Amphiboly • Example: I am

opposed to taxes which slow economic growth.

FALLACIES OF AMBIGUITY

• Composition• This fallacy is a result

of reasoning from the properties of the parts of the whole to the properties of the whole itself--it is an inductive error.

FALLACIES OF AMBIGUITY

• Composition• Example: Sodium and

Chloride are both dangerous to humans. Therefore any combination of sodium and chloride will be dangerous to humans. (Sodium Chloride = salt)

FALLACIES OF AMBIGUITY

• Division• This fallacy is

misapplication of deductive reasoning. One fallacy of division argues falsely that what is true of the whole must be true of individual parts.

FALLACIES OF AMBIGUITY

• Division• Example: "Minorities get

paid less than 'whites' in America. Therefore, the black CEO of a multi-billion dollar company gets paid less than the white janitor who cleans his office."

COMPONENT FALLACIES

•Component fallacies are errors in inductive and deductive reasoning.

COMPONENT FALLACIES

•Deductive is where facts are determined by combining existing statements,

COMPONENT FALLACIES

•While Inductive is where facts are determined by repeated observations.

COMPONENT FALLACIES

• Begging the Question

• Writers assume as evidence for their argument the very conclusion they are attempting to prove.

COMPONENT FALLACIES

• Circular Reasoning • Often the writers

using this fallacy take one idea and phrase it in two statements. The assertions differ sufficiently to obscure the fact that that the same proposition occurs as both a premise and a conclusion.

COMPONENT FALLACIES

• Hasty Generalization• Making assumptions

about a whole group or range of cases based on a sample that is not a good example, usually because it is atypical or just too small. Another common example of this fallacy is the misleading statistic.

COMPONENT FALLACIES

• Straw Man Argument• This fallacy includes

any lame attempt to "prove" an argument by overstating, exaggerating, or over-simplifying the arguments of the opposing side.

COMPONENT FALLACIES

• Slippery Slope• The arguer claims

that a sort of chain reaction, usually ending in some dire consequence, will take place, but there's really not enough evidence for that assumption.

COMPONENT FALLACIES

• False Dilemma - Either/Or

• This fallacy occurs when a writer builds an argument upon the assumption that there are only two choices or possible outcomes when actually there are several.

FALLACIES OF OMISSION

• These errors occur because the logician leaves out necessary material in an argument or misdirects others from missing information.

FALLACIES OF OMISSION

• Stacking the Deck or Fallacy of Exclusion

• In this fallacy, the speaker ignores examples that disprove the point, and lists only those examples that support her case.

FALLACIES OF OMISSION

• Argument from the Negative

• Asserts that since one position is untenable (incapable of being defended, as an argument, thesis, etc.; indefensible), the opposite stance must be true.

FALLACIES OF OMISSION

• Appeal to a Lack of Evidence or Argument from Ignorance

Arguing that, since the opposition cannot disprove a claim, the opposite stance must be true.

FALLACIES OF OMISSION

• Hypothesis Contrary to Fact

• Trying to prove something in the real world by using imaginary examples alone, or asserting that, if hypothetically X had occurred, Y would have been the result.

FALLACIES OF OMISSION

• Hypothesis Contrary to Fact

• Example: suppose an individual asserts that if Einstein had been aborted in utero, the world would never have learned about relativity, or that if Monet had been trained as a butcher rather than going to college, the impressionistic movement would have never influenced modern art.

FALLACIES OF OMISSION

• Contradictory Premises

• If the definitions of two terms conflict with or exclude each other, then those two terms cannot be simultaneously ascribed to a single object or event.

Logical Fallacies

• Remember that these types of persuasion are used in media because they appear to be legitimate arguments.

• Be aware of these and you will not be fooled!