Post on 11-Jan-2016
1
Discourse Fallacies
PSC 202Fall 2004Prof. Northrup
2
Formal and Informal Fallacies
FallacyFormal fallacyInformal fallacy
3
Informal Fallacies – Four Types
I. Fallacies of Ambiguity
II. Fallacies of Relevance
III. Fallacies of Presumption
IV. Fallacies of Weak Induction
4
I. Fallacies of Ambiguity (5)
Based on ambiguous use of terms or phrases
That is, the term or phrase can have more than one meaning
5
I. 1) Equivocation
A shift in meaning of a word in one premise to the next, or from a premise to the conclusion
E.g.All cats are small domestic animals
All lions are cats
So, all lions are small domestic animalsCan be done conversationally
6
I. 2) Amphiboly
Like equivocation, but applies to a phrase
The meaning of the phrase shiftsExample: Methodists and “doubt”
Leader: Rise and greet the morning.People: Cast off your sleep and doubt.
7
I. 3) Accent
Occurs when a passage is incompletely quoted or a passage is taken out of context or both
Examples:Sound bitesTaking only words that support your side
8
I. 4) Division
When a claim that is true of an entire class of things is mistakenly applied to a single member of the class, OR
A claim that is true of a whole thing is mistakenly applied to a part of a whole
Example: state vs. national trends
9
I. 5) Composition
The mirror image of division Inferring that a whole or an entire class of
objects has certain properties because one of the parts of the whole, or one member of the class, has that property
Examples: “Because of hurricane Ivan, there was flooding
in Louisiana today.” “The hood of my car is red, so my car is red.”
10
II. Fallacies of Relevance (8)
Assume a false premise or reach a conclusion that is not supported by the premises
Often used by politicians
11
II. 1) Appeal to Force
Argumentum ad baculumAn argument includes an implicit but
unwarranted or inappropriate threatConsider:
“You should make a contribution to the Democratic candidate. After all, you are currently an employee of this company.”
12
Appeal to Force - Caveat
Not a fallacy if the threat is legitimateConsider:
“Watch your speed. Police use radar.”
13
II. 2) Personal Attack
Argumentum ad hominemOccurs when replying to an argumentThe person, not the argument, is
attackedCalling credibility into question
14
Personal Attack continued 1
Tricky – sometimes valid to question E.g. “expert” witness in a trial
Example? Campaign strategy of accusing opponent of flip-flopping
15
Personal Attack continued 2
Tu quoque (literally, “you too”) “You do it, why shouldn’t I?”
Sarcasm as a response “I see you've set aside this special time to
humiliate yourself in public.”
16
II. 3) Mob Appeal
Argumentum ad populum Assumption that some type of popular appeal
is a sufficient reason to engage in an action or hold a belief
Typical forms Inclusion: “Doing x (e.g. voting for this candidate)
makes you feel good, so you should do it.” Exclusion: Not doing x excludes you from the norm
(of the mob) Appeals to emotion (e.g. Hitler’s speeches) “Family values”?
17
II. 4) Appeal to Pity
Argumentum ad misericordium Assumes that suffering is a sufficient reason to
engage in an action or hold a belief (e.g. charity call) Possibly valid moral reason but irrational solution Or may not be a cause for pity
So must ask two questions: Is there moral force to the claim of suffering Is the solution a good one
18
II. 5) Stereotyping
General claim about a group that is falsebecause
1. not true of that group There was a blonde, a red-head and a brunette…”
2. not more true of that group than any other “Red-heads have bad tempers”
3. claim has some validity but not of the group’s making Northern Ireland – Protestant claim that Catholics
are lazy because they don’t get jobs Also called the genetic fallacy
19
II. 6) Straw Man
When an argument is misrepresented and the misrepresentation is criticizedCan be done by claiming that there is an
underlying premise that you have now revealed, and it’s wrong
Can be done by misrepresenting the conclusion, and then criticizing the conclusion
20
II. 7) Red Herring
A response to an argument that confuses the issues, thus causing a distraction from the actual
argumentSmith factory exampleDistraction may be a valid concern, but
doesn’t address the argument at hand
21
II. 8) Irrelevant Conclusion
non sequitur (doesn’t follow)When a conclusion is drawn from an
argument not suggested by the premisesObvious example - an invalid deductive
argument:All aardvarks are mammalsAll mammals are vertebratesSo, some aardvarks are good pets
Hunting example
22
III. Fallacies of Presumption (4)
Assumes something that isn’t stated and does so incorrectlyassumes the conclusion as a premiseassumes that the premises contain all the
relevant information while they do notUnlike a deductive argument where the
premises entail the conclusion, that is, the premises logically result in the conclusion
23
III. 1) Begging the Question
Conclusion is assumed as one of the premises “George Bush is the President because George
Bush is President”
Different words, same meaning “George Bush is the President of the US, since
George Bush holds the highest office in the US”
True, but proves nothing Circular argument: made up of several
arguments where the conclusion of the last is a premise of the first
24
III. 2) Complex Question
Assumes a previous question has been answered “How long have you been cheating on tests?”
Question by itself doesn’t constitute a fallacy; has to be part of an argument
An implicit argument can often by found in a question (immigration example)
Caveat: Not a complex question if embedded in a longer argument where the premises are explicitly stated
25
III. 3) Suppressed Evidence
When you know there is evidence contrary to your position, yet you suppress the evidence
E.g. tobacco companies
26
III. 4) False Dichotomy
Occurs in the case of a disjunctive syllogism (either/or argument)Maria is either a Democrat or RepublicanMaria is not a DemocratSo she is a Republican
If disjunctive premise is false, the conclusion is false
Example: 1950s motto, “Better dead than red”
27
IV. Fallacies of Weak Induction
Remember = inductive arguments are probable arguments
Fallacy occurs when insufficient evidence is provided
Weak induction fallacies occur when evidence cited is weak or incompleteevidence contrary to the conclusion is
ignored
28
IV. 1) Appeal to Authority
Incorrect use of authorityAssuming authority in one field implies
authority in anotherAppeal to something as an authority (e.g.
custom, popular opinion) when it is not
29
IV. 2) Appeal to Ignorance
A claim is made, either that since there isn’t any evidence that a
proposition is false, it must be true, or that since there isn’t any evidence that the
proposition is true, it must be falseNuclear power plant exampleCaveat: Some statements can look like
an appeal to ignorance but aren’t
30
IV. 3) Hasty Generalization
When a conclusion is reached on the basis of insufficient evidence
Can happen when a conclusion is drawn from an atypical sample or too small a sample
31
IV. 4) False Cause
Something is taken to be a cause when it isn’t (non causa pro causa, “not a cause as a cause”) Advertising tactic
1. One event follows another; first event is identified as the cause (post hoc ergo propter hoc, “before therefore because”) e.g. superstitions
2. Single cause identified but a complex situation Ronald Reagan ended the Cold War
32
IV. 5) Slippery Slope
Chain of causal claims with one or more of them false
Often characterized by consequences getting progressively worseCigarettes lead to heroin
Caveat: There are valid causal chainsPolitical issues like gun control - slippery
slope or not?
33
IV. 6) Weak Analogy
An argument that uses analogy to persuade, but where there are ways in which the points of
comparison are insufficient to support the claim or
there are significant non-analogous points among the things compared