Philosophy Exam 2 - Logical Fallacies and Types of Arguments Flashcards
Deduction and Induction mean the same as.
Necessity vs. Probability
Deductive Arguments
it is impossible for the conclusion to be false if the premises are true; True Premises = True Conclusion (Cannot be False)
Inductive Arguments
It is improbable that the conclusion is false if the premises are true; True Premises = Probably True Conclusion (Probably not False)
All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal. Deductive or Inductive?
Deductive
Common _______ Argument: Based on Mathematics
Deductive Argument;
Since X + Y = 10,
and X = 7,
it follows that Y = 3.
NOT STATISTICS
Common ________ Argument: From Definition
Deductive Argument;
Because Claudia is mendacious, it follows that she tells lies.
Common ________ Argument: Categorical
Deductive Argument;
All flowers are plants.
All Daises are flowers.
Therefore, all daises are plants.
Common ________ Argument: Hypothetical
Deductive Argument;
If inflation heats up, then interest rates will rise. If interest rates rise, then bond prices will decline. Therefore, if inflation heats up, then bond prices will decline.
Common ________ Argument: Disjunctive Syllogisms
Deductive Argument;
Either global warming will be arrested, or huricanes will become more intense.
Global warming will not be arrested.
Therefore, hurricans will become more intense.
The sun has risen everyday for the last 2,000 years.
Therefore, probably, the sun will rise tomorrow.
Deductive or Inductive?
Inductive
Common _______ Argument: Prediction
Inductive Argument;
I have always seen sunflowers bloom in summer in this valley.
Therefore, I will see sunflowers bloom in this valley next summer.
Common _______ Argument: Analogy
Inductive Argument;
Because Christina’s porshe is a great handeling car, it follows that Angela’s porshe must also be a great-handeling car.
Common _______ Argument: From Authority
Inductive Argument;
Isaac Newton was a great scientist and an alchemist, so we should take the discipline of alchemy seriously.
Common _______ Argument: Based On Signs
Inductive Argument;
The Broadway marquee says that “Phantom of the Opera” is playing nightly. Therefore, itmust be the case that “Phantom” is playing there tonight.
Common _______ Argument: Causal Inference
Inductive Argument;
From the knowledge that a bottle of wine had been accidentally left in the freezer overnight, someone might conclude that it had been frozen.
Valid/Invalid Arguments only apply to:
Deductive Arguments
Strong/Weak Arguments only apply to:
Inductive Arguments
Sound/Unsound Arguments only apply to:
Deductive Arguments
Cogent/Uncogent Arguments only apply to:
Inductive Arguments
Valid Argument
IMPOSSIBLE for conclusion to be false if premises are true (Deductive)
Invalid Argument
IS POSSIBLE for conclusion to be false if premesis are true (Deductive)
Soundness of an Argument
Validity + All true premises
To test for validity…
Assume all premises are true. From that assumption, find out whether the conclusion is also true.
Strong Argument
IMPROBABLE for conclusion to be false if premises are true (Inductive)
Weak Argument
Conclusion does not follow PROBABLY from the premises, despite claiming it does (Inductive)
Cogentcy of an argument
Strong + All true premises
To test for strength…
Assume all premises are true. From that assumption, find out whether the conclusion is also probably true.
(D or I?)
This marble from the bag is black. Another marble from the bag is black.
A third marble from the bag is black. Therefore all the marbles in the bag are black.
Inductive, Weak, Uncogent
(D or I?)
All men are mortal.
Joe is a man.
Therefore Joe is mortal.
Deductive, Valid, Sound
(D or I?)
Mr. Hill is a jackass.
All jackasses have long ears. Therefore, Mr. Hill has long ears.
Deductive, INVALID (because of logical fallacy EQUIVOCATION), Unsound. It would be VALID if the word ‘Jackass’ was meant the same way in both premises
(D or I?)
All dogs have four legs.
All dogs are animals.
Therefore all animals have four legs
Deductive, Invalid, Unsound
(D or I?)
All dogs are animals.
Rover is a dog.
Therefore Rover is an animal.
Deductive, Valid, Sound
(D or I?)
Daffy Duck is a duck.
All ducks are mammals.
Therefore, Daffy Duck is a mammal.
Deductive, Valid, Unsound
(D or I?)
Most birds can fly.
Tweety is a bird.
Therefore, Tweety can probably fly.
Inductive, Strong, Cogent
(D or I?)
All meteorites found to this day have contained salt.
Therefore, probably the next meteorite to be found will contain salt.
Inductive, Strong, Uncogent
Modus Ponens
If P then Q.
P.
Therefore, Q.
Valid.
Modus Tollens
If P, then Q.
Not Q.
Therefore, not P.
Valid.
Affirming the Consequent
If P then Q.
Q.
Therefore, P.
Invalid
Fallacy
A mistake in reasoning; a defect in an
argument that consists of something other than merely false premises.
Formal Fallacy
A fallacy identified by merely examining the form or structure of an
argument (Affirming the Consequent: If P then Q, Q, Therefore P).
Informal Fallacy
A fallacy that can only be identified by examining the content of the argument.
Fallacies of Relevence
Arguments where premises
are logically irrelevant to the
conclusion, but the premises
may appear to be psychologically relevant, so the conclusion may seem to follow. Appeal to Force, Pity, and People (ad Populum).
Appeal to Force
An arguer poses a conclusion to another person and tells that person either implicitly or explicitly that some harm will come to him if he does not accept the conclusion.
F:
Jordan: Dad, why do I have to spend my summer at Jesus camp?
Dad: Because if you don’t, you will spend your entire summer in your room with nothing but your Bible!
Appeal to Force (Fallacy of Relevence)
Appeal to Pity
The arguer attempts to support a conclusion merely by evoking pity from the reader or listener.
F:
You need to pass me in this course, since I’ll lose my scholarship if you don’t.
Appeal to Pity (Fallacy of Relevance)
Appeal to the People (ad Populum)/Bandwagon
A speaker uses desires like being loved, esteemed, admired, valued, recognized, and/or accepted by others to get the reader of listener to accept a conclusion.
F:
Twilight must be a great book because everybody seems to have read it.
Appeal to the People (Fallacy of Relevance)
Ad Hominem
The claim that the speaker is certain kind of person is the reason for thinking the argument is bad (or should be dismissed).
Three types of Ad Hominems:
Abusive - the second person responds to the first person’s argument by verbally abusing the first person.
Circumstancial - the opponent hopes to discredit the speaker’s argument by alluding to certain circumstances that affect the speaker.
“You too” - the opponent attempts to make the speaker appear hypocritical, or as arguing in bad faith. This is usually done by citing features of the speaker’s life that conflict with the speaker’s conclusion.
F:
Tony wants us to believe that the origin of life was an “accident”. Tony is a godless SOB who has spent more time in jail than in church, so the only information we should consider from him is the best way to make license plates.
Ad Hominem (Abusive)