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FOCUS ON LOGOS
Formulating a logical argument using
Inductive and Deductive Reasoning
Rhetorical Triangle
Appeals to Logic (logos)
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Theoretical, abstract language
Denotative meanings/reasons
Literal and historical analogies
Definitions
Factual data and statistics
Quotations
Citations from experts and authorities
Informed opinions
• ARGUMENT = CLAIM +
SUPPORT FOR CLAIM
• Arguments use either
DEDUCTIVE or INDUCTIVE
reasoning.
Deductive Arguments
• argument from the general to the
particular.
• leads to certain conclusions.
• arguments are valid or invalid.
Examples of Deductive Reasoning
All men are mortal (major premise)
Socrates was a man (minor premise)
Therefore Socrates was mortal. (conclusion)
If it rains, the sidewalks become wet
It is raining
Therefore the sidewalks are wet.
…Deductive reasoning contd.
All women are brilliant. (major premise)
I am a woman. (minor premise)
Therefore, I am brilliant. (conclusion)
Everyone who has been exposed to the Ebola
virus has died.
John Q. has been exposed to the Ebola virus.
John Q. will die.
Inductive Arguments
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argument from particular
observations to general conclusions.
leads to probable conclusions, not
necessary ones.
arguments can be better or worse
depending on degree of probability.
Examples of Inductive Reasoning
Socrates was Greek’
Most Greeks eat fish
Socrates ate fish.
Eddie has failed to follow through with his
education, in his relationships with women,
and with the jobs that he has previously held,
therefore he will probably not follow through
on this assignment.
Inductive Arguments contd.
Many people who smoke seem to get
cancer.
Thus, if you want to avoid getting
cancer, don't smoke.
Logical Fallacies
(p. 631 in RCWW)
Example:
• Why is counterfeiting illegal? I’ll tell you
why. It is because it is against the law!
• We sin, because we are sinners.
LOGICAL REASONING
EXERCISE:
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Penguins make great pets.
Milk should be banned.
People really don’t need skin.
The new pizza diet is wonderful.
Tabloids should replace texts.
Humans should always go barefoot.
Hot-air balloons make great commute
vehicles.
8. Children should be able to vote.