Philosophy
6: Logic in Practice
Los Angeles Pierce College
Department of History, Philosophy, & Sociology
Lecture Notes
Lecture Notes for
"Chapter Six" of Porter's The
Voice of Reason
Fallacy of Sweeping Generalization
"The informal fallacy
of sweeping generalization consists of using one statement in an all-inclusive
way without allowing for any exceptions."
Fallacy of Sweeping Generalization E.G.
Lying is never a good
option.
Nobody likes pain.
Fallacy of Sweeping Generalization / Accident
"Here the qualities
that apply to the whole are assumed to apply to the parts, without allowing for
the "accidental" circumstances that make it inapplicable."
From whole to parts
"But what is true of
the whole may not be true of the parts"
Fallacy of Sweeping Generalization / Accident E.G.
"if the United States
consumes more pasta than Italy, that does not imply that each American eats
more pasta than each Italian does."
"Salt is necessary
for life! So make sure to consume
some sodium, and make sure to consume some chlorine.
Fallacy of Sweeping Generalization / Hasty Generalization
"the fallacy of
making a broad generalization on the basis of insufficient number of
instances."
Hasty Generalization E.G.
"Whenever you are inclined
to say, 'if you've seen one, you've seen them all,' we are probably leaping to
conclusions."
Fallacy of Sweeping Generalization / Converse
Accident
"Here it is
erroneously assumed that what's true of the parts is true of the whole when, in
fact, new factors may arise when a group is formed, giving it different
characteristics."
Fallacy of Sweeping Generalization / Converse Accident
E.G.
"since Italians as
individuals eat more past than Americans, Italy consumes more pasta than the
United States."
"Don't put salt on
your food! Don't you know that
sodium can be explosive, and chlorine is poisonous!?!"
Accident & Converse-Accident
"Often the
characteristics of the group and those of its members do not
coincide."
Trying it Out
IV. 1
IV. 2
IV. 4
Begging the Question
"The fallacy of
begging the question is a circular argument in which we already assume the point
we are trying to prove."
Begging the Question E.G.
"A well-known modern
illustration of begging the question in Joseph Heller's book Catch 22. In this book the main character says,
'Let me get this straight. In order
to be grounded I have to be crazy.
And I must be crazy to keep flying.
But if I ask to be grounded that means I'm not crazy and I have to keep
flying.' Obviously this is a
circular argument that produces a double bind."
Complex Question / Take One
"when a single
question actually contains several others, so that answering one question entails
a number of different admissions."
Complex Question / Take One E.G.
"The most famous
example is that of the prosecutor who asks, 'Have you stopped beating your
wife?'"
"If the accused
person answer 'yes,' he is admitting that he beat his
wife before."
"If he says 'No,'
that means his continuing to beat her."
"The hidden and prior
question is whether he ever beat his wife at all."
"If the accused
person tries to raise this objection he may be criticized for quibbling and
trickiness or making fine distinctions, evading the issue."
"The prosecutor may
insist that he 'just answer the question, yes or no,' but a simple yes or no
would be self-incriminating either way."
Complex Question / Take Two
"when a question has
two parts and we are asked to respond to both with a single answer."
Complex Question / Take Two E.G.
Aren't fanged unicorns
fascinating and cuddly?
Handling A Complex Question
"We must take the
questions one at a time, and refuse to answer the second until we settle the
first one that it depends on."
Trying it Out
IV. 3
IV. 6
VII. 3
VII. 4
VIII. 3
Argument from Ignorance
"The argument from
ignorance (argumentum ad ignorantiam)" assumes
"that a statement is true because it has not been proven false, or that it
is false because no one has proven it true."
"In technical terms,
we cannot start with negative premises and reach any positive conclusions;"
"beginning with 'I
don't know' we cannot end up with 'Therefore, I know.'"
"it is a fallacy to
believe that what we don't know can be used as an argument for or against some
conclusion."
Argument from Ignorance / Converse
"Conversely, we
cannot assume a position is false because no one knows 'for sure' that it is
true."
"To reject a position
we must disprove it, not just call it wrong in the absence of proof that it is
right."
Argument from Ignorance / Converse E.G.
"For example, it
would be a mistake to argue that the theory of evolution is incorrect because
biologists have not proven it beyond all doubt."
Argument from Ignorance / Absence of Proof
"the absence of proof
is not in itself disproof, any more than the absence of disproof can be taken
as proof."
"We cannot claim that
angels do not exist because no one has shown that they do."
Argument from Ignorance / Exception
"In law, for example,
when a person is accused of a crime, the person is presumed innocent until
proven guilty, sometimes 'beyond a shadow of a doubt.'"
"The lack of proof of
a person's guilt is taken to mean the person is not guilty."
Argument to the Masses
"The argument to the
masses (argumentum ad populum) makes an emotional
appeal to the general public emphasizing our basic heritage, the deeply held
attitudes and symbols of our society."
Argument to the Masses / Psychological Appeal
"On a psychological
level the argument appeals to our desire to belong, to be part of a group with
values and beliefs in common."
Argument to the Masses / E.G.
"'We're all loyal
Americans here, and we know how many young lives have been lost fighting to
safeguard our freedom. If we have
any respect for this great country or ours and for those who made the supreme
sacrifice, we must vote against federal regulations that limit our rights as
free citizens. All real patriots
must join me in opposing this encroachment on our hard-won
liberties.'"
Parentisims
"Proverbs, adages,
and old saws are often used to persuade us to accept ideas we might otherwise
reject."
"The implication is
that these truths are basic and self-evident, and we would be foolish to go
against tried and true knowledge."
Parentisims / E.G.s
"Look before you leap" "He
who hesitates is lost"
"Many hands make
light work" "Too
many cooks spoil the broth"
"Better safe than
sorry" "Nothing ventured, nothing gain"
"If it's not broken,
don't fix it"
"A stitch in time saves nine"
"You can't teach an
old dog new tricks" "It's never too late to learn"
"Out of sight, out of
mind" "Absence
makes the heart grow fonder (Familiarity breeds contempt)"
Bandwagon
"Sometimes the
argument to the masses is called the 'bandwagon' technique, especially when
everyone is urged to go along with the crowd."
Bandwagon / Problem
"We cannot establish
truth by counting heads or taking polls."
"This is the fatal
flaw in the bandwagon approach and in the argument to the masses in
general."
False Cause
"incorrectly
identifying one event as causing another, that is compelling it to happen
again."
"The usual form of
this fallacy is to think that because one occurrence precedes another, the
first must be the cause of the second."
"An unrelated
sequence of events is confused with a cause-effect relationship."
False Cause Humorous E.G.s
"Most people today do
not die at home but rather in a hospital; however, this does not mean that
hospitals are responsible for people's deaths."
"Such reasoning is
faulty as thinking that since people usually die in bed, the way to avoid death
is to sleep on the couch."
"Obviously, beds do
not cause death even though people may die after taking to their
beds."
False Cause Serious E.G.
"A very destructive
mistake about causation was made in the 1930's. A Dr. Manfred Sakel
developed a successful treatment for schizophrenics that involved large doses
of insulin, which produced convulsions.
Other psychiatrists then tried to duplicate the convulsions using
electric shock treatments, but their patients actually deteriorated. Their mistake was to assume that the
convulsions were the reason for the cure, when in fact they were only a side
effect. The treatment worked
because the insulin restored the patients' chemical balance."
Irrelevant Conclusion
"Irrelevant
conclusion ... is a generic or catchall category, and simply means that the
conclusion of an argument does not follow from the premises offered for
it."
"Sometimes it is
called a non sequitur, meaning simply that the conclusion does not
follow."
"the conclusion is
irrelevant to the premises."
Resonance
"The fallacy of
irrelevant conclusion can include a number of the fallacies already
described."
Argument to the person
Argument from authority
Appeal to pity
Straw person
Begging the question
Gambler's fallacy
Argument from ignorance
Argument to the masses
False cause
Irrelevant Conclusion E.G.
1) Cleanly shaven, fanged
unicorns haunt the internet
2) I was house-trained
before I was potty-trained
Therefore
3) You'll do well on
today's logic quiz
Trying it Out
IV. 1-5