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the fallacy tree
Transcript of the fallacy tree
1. Appeal to emotion
2. Red Herring
3. Straw man
4. Attack on the person
5. Appeal to force
6. Missing the point (irrelevant conclusion)
4.4 Fallacies of defective induction
1. Argument from ignorance
2. Appeal to inappropriate authority
3. False cause
4. Hasty Generalization
4.5 Fallacies of Presumption
(fallacy of ignoring exception)
2. Complex Question
(incriminating question; (= plurium interrogationum)
3. Begging the Question (assuming the conclusion)
4.6 Fallacies of Ambiguity
1. Equivocation (lexical ambiguity)
2. Amphiboly (structural ambiguity)
Questions and quizzes
What is a fallacy?
With fallacies of defective induction, the premises are relevant to the conclusion, but do not force the conclusion.
1. Argument from ignorance
2. Appeal to inappropriate authority
3. False cause
4. Hasty Generalization
This is when an arugment has the premise 'we just don't know', and the conclusion 'So ......... must be the case'.
This is a fallacy because the only thing you can assert from claiming ignorance, is more ignorance.
For example, 'We cannot prove that the Flying Spaghetti Monster doesn't exist, therefore, Flying Spaghetti Monster must exist'
The Celestial Teapot
Which of these, if any, are arguments from ignorance?
1) I can't see you, therefore, you do not exist.
2) I can't see you, therefore, you do exist.
3) The cat is either dead or alive and not both, therefore I will only know when I observe the cat.
4) The existence of unicorns has not yet been disproved. This is evidence for the existence on unicorns.
Which of these, if any, are an appeal to inappropriate authority?
1) My careers adviser says that a degree will help me get a job, therefore, I should finish my degree.
2) One million women bought this product, therefore this product is good.
3) A lot of celebrities are on this diet, therefore I should be on this diet.
This fallacy consists in referring to someone who has authority in some area, but is not necessarily an expert in the relevant topic, in order to strengthen your own claim.
This is flawed because the causation could have happened in the other direction, they could both have a third common cause, or it could be simple coincidence.
Which of these, if any, are fallacies of false cause?
1) Winter arrives and birds fly south. Therefore, the actions of the birds caused winter to arrive.
2) I took some medicine, and my illness went away. Therefore, my illness went away because I took the medicine.
3) Studies show that those children who start drinking coca-cola sooner, are more likely to 'fit in' at school. Therefore, coca cola improves children's social abilities.
This fallacy occurs when one event follows another event, or they happen at the same time, and the conclusion is that one event must have caused the other.
Example in action...
Note: Having cameras pointing in your direction is not equivalent to knowing about cameras.
This is flawed because a) they may have expertise in a totally different field, and b) even if they are experts on the relevant topic, their arguments are not necessarily sound.
"When an argument relies on premises that are not relevant to its conclusion, and that therefore cannot possibly establish its truth, the fallacy committed is one of relevance."
- Copi & Cohen, "Introduction to Logic", 10th ed., 1998, New Jersey, Chapter 6.2: Fallacies of Relevance, p.162
"This is fallacious because it replaces the laborious task of presenting evidence and rational argument with expressive language and other devices calculated to excite enthusiasm, excitement, anger, or hate."
- Copi & Cohen, "Introduction to Logic", 10th ed., 1998, New Jersey, Chapter 6.2: Fallacies of Relevance, R4. The appeal to emotion: Argument Ad Populum, p.169
"The fallacy of proving a conclusion not pertinent and quite different from that which was intended or required."
- Philosophy 103: Introduction to Logic
Ignoratio Elenchi, http://philosophy.lander.edu/logic/ignoratio.html
Fallacies of presumption are not errors of reasoning in the sense of logical errors.
Fallacies of presumption begin with a false (or at least unwarranted) assumption and so fail to establish their conclusion.
2. Complex Question
3. Begging the Question
The fallacy of Accident occurs when a rule that is generally applicable is applied to an exceptional case and the exceptional character of the case is ignored.
+ Women earn less than men for doing
the same work.
+ Oprah Winfrey is a woman.
+ Therefore, Oprah Winfrey earns less than
male talk-show hosts.
The 'celestial teapot' was an argument made by Bertrand Russell, to highlight this fallacy.
Which of these, if any, are examples of an Accident fallacy?
1) Cutting people with knives is a crime. Surgeons cut
people with knives. So, surgeons are criminals.
2) The law states that one should not drive faster
than 100 km per hour. Therefore, even when the
road is empty and you are rushing an emergency
patient to the hospital you should not drive
faster than 100 km per hour.
3) A man refuses to drink alcohol even when asked
by the doctor on the ground that alcohol is
4) A man has been prescribed to drink alcohol when
he was ill reasons that it would be alright to
continue taking it even after getting well.
This fallacy occurs when someone demands a single
answer to a complex question.
Example: Have you stopped beating your wife?
--> Both the answers ‘yes’ and ‘no’ will imply that you have at some point beaten your wife.
Which of the following questions, if any, are complex questions?
1. What hair dye are you using?
2. Do you prefer to go out, watch a movie or to stay home and have a drink?
3. Where are you hiding the money you have stolen?
4. If God did not create the universe, who did?
Begging the question is the fallacy of using the conclusion of an argument as one of the premises offered in its own support.
Example: A: God must exist
B: How do you know?
A: Because the Bible says so.
B: Why should I believe the Bible?
A: Because the Bible was written by
"If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense."
Obama: ‘Good morning!’ * walks toward the door of his office *
Security: ‘Excuse me, didn’t you see the sign ‘No enter’?
Which of these, if any, are examples of ‘Begging the Question’?
1) Murder is morally wrong. Therefore, abortion is morally wrong.
2) Opium induces sleep because it has a soporific quality.
3. John is coming to the party tonight because he wants to go out.
This fallacy occurs when one mistakes insufficient evidence for sufficient evidence.
This might be phrased in the form "there are some indicators that ....... is the case, therefore ...... is the case"
This is a flawed argument because we know that all P objects have the quality of Q, however not everything with the quality of Q is necessarily a P
Which of these, if any, are fallacies of hasty generalization?
1) All swans that I have seen are either black or white, therefore it is possible that all swans are either black or white
2) All cats are mammals. Tigger is my pet cat, therefore Tigger is a mammal.
3) I know that this statement is a fallacy. Therefore, everyone should realize that this statement is a fallacy.
A fallacy is an argument which is not valid, but is 'psychologically persuasive'.
This means that, while the premises do not force the conclusion, we are inclined to agree with them for some emotional reason.
It is important to understand fallacies, as in many discussions and philosophical works you will come across a countless number of these invalid arguments. Also, If you are aware of these mistakes, you are les likely to make them in your own arguments.
Try and work out what fallacies are being used in each example
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This is a Necker cube.
A Necker cube is an ambiguous line drawing.
Ambiguity occurs in language when there are multiple possible interpretations of language elements: a word, grammatical construction, context etc.
Fallacies of ambiguity occur when an argument relies on a switch of interpretations in order to be convincing.
Occurs when an argument relies on a switch of interpretation of a word.
There are more than one ways of interpreting the drawing.
We can only interpret the drawing in one way at a time.
Statements like ''This is a Necker cube' is written on the foremost side of the cube' are true only in some interpretations.
Prompt: visual ambiguity
Ambiguity in language and argument
Note well: ambiguity vs. vagueness
Ambiguity is not the same as vagueness. Vagueness has a technical definition in philosophy. Thereby, a statement like 'Buffalo buffalo buffalo Buffalo buffalo' has an indeterminate meaning until I tell you that 'Buffalo, the animal [from] Buffalo buffalo [verb: to bully] buffalo, the animal, [from] Buffalo'. The meaning is now clear and unambiguous, while there was no apparent meaning in the beginning.
Example in C&C, from Lewis Carroll's writing:
“Who did you pass on the road?” the King went on, holding out his hand to the Messenger for some more hay.
“Nobody,” said the Messenger.
“Quite right,” said the King: “this young lady saw him too. "So of course Nobody walks slower than you."
“I do my best,” the Messenger said in a sulky tone. “I’m sure nobody walks much faster than I do!”
“He can’t do that,” said the King, “or else he’d have been here first.”
When an argument relies on an interpretation of an ambiguous grammatical structure.
Candy grab time: your favourite example.
Note well: relative terms
Some terms, like 'tall' are relative terms. A tall person is someone who is taller than most people, a tall building- one taller than most buildings. A short building is still taller than most people, so keeping your relative terms clear is important. One way to do it is to keep an 'is taller than' list of relations.
'John was lying on a bed without one leg.'
'Competent women and men should apply'
'Walt will diet and exercise only if his doctor approves.' [Source: CDP: 'ambiguity']
Indicated by dangling participles.
Participles are words formed from a verb, and used as an adjective of some subject.
In cases of dangling participles it is unclear which is the subject of the adjective.
Provide an example.
When an argument relies on a change in the interpretation of context.
Change in emphasis:
'We should not speak ill of our friends.'
'We should not speak ill of our
'We should not
ill of our friends.'
Taking someone's words out of context, then relying on the change to argue that someone holds some belief.
Original quote: 'It is silly to believe that I am an extraterrestrial.'
Headline: ''I am an extraterrestrial', person claims.'
When an argument relies on a change in the interpretation of reference to parts of a whole to an interpretation of reference to the whole. Alternatively, it relies on a change in the interpretation of reference from members of a class to the class itself.
'The human body is made up of cells, which are invisible.
Therefore, the body is invisible.'
Note well: Distributive versus Collective
We may say that 'students enroll in hundreds of modules each term', but only if we are using 'students' collectively: i.e. referring to the class of all students.
We may say that 'Students enroll in no more than ten modules each term' only if we are using 'students' distributively: i.e. reffering to each student individually.
When an argument relies on a change in the interpretation of reference from a whole to an interpretation of reference to parts of the whole. Alternatively, it relies on a change in the interpretation of reference from a class to the reference to the members of that class.
All of the parts of the object O have the property P.
Therefore, O has the property P.
(Where the property P is one which does not distribute from parts to a whole.)
The fallacy of division is similar to the fallacy of composition, but in the other direction: from the whole to its parts (or from the class, to its members).
H2O is water which is a liquid. This means that molecules H20 are also liquids. However, this is not the case because alone H is hydrogen and O is Oxygen. Together these molecules form a liquid. However, taken as separate molecules both of these are gases. [Source: fallaciesfiles.weebly.com/fallacy-of-division.html ]
The fallacies of composition and division do not correspond to converse accident and accident, respectively.