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Lecture 2

MODR 1760 Lecture Notes - Lecture 2: Presupposition, Begging, Perjury


Department
Modes Of Reasoning
Course Code
MODR 1760
Professor
Hilary Davis
Lecture
2

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Fallacies 15/09/2011 10:31:00 AM
Truth
Whether or not premises and conclusions correspond to fact
Validity
Relationship of the premises to the conclusion
Whether reasoning makes sense
Soundness
When premises are true and conclusion validly derived from them
Conclusion is the logical consequence of the premise
o All men are mortal
o Socrates is a man
o Therefore, Socrates is mortal
Unsound arguments
True premises but invalid connection to conclusion
o Just because “a” is “b” and “c” is “b”, does not make “a” “b”
Valid reasoning but untrue premise
o All dogs are ferocious
o Tom has a dog, Shaggy
o Therefore, Shaggy is ferocious
Untrue premise and invalid reasoning
o I like this course
o All final exams are easy
o Therefore, I will receive a high grade in this course
Necessity and Sufficiency
When evaluating an argument, ask yourself if the premises are
necessarily true
o Do both premises both have to be there for an argument to
be true?
Are premises sufficient to prove the conclusion
o Is there enough evidence?
Evaluating Arguments
Interested in whether an argument is sound:
o Are premises true or acceptable to a reasonable person?
o Is the reasoning to arrive at the conclusion valid?
Not interested in
o Clarity, elegance, persuasiveness, or economy of style
Do not be opinionative

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We do not need to know if conclusion is true
Fallacies
Illusion of a good argument
Must be explained, not simply identified
Even when an argument is contains fallacies, the conclusion may be
true
1. Appeal to Force or Threat of Force (Appeal to Fear)
instead of using reasons this fallacy threatens to use force to get
another to do something or accept an idea
2. Appeal to Emotion
persuade us by manipulating our emotions/desires
o emotions usually irrelevant to issue
Appeal to Pity
Appeal to Fear
Appeal to Guilt or Shame
Appeal to Flattery
3. Ad Hominem (“To the man”)
the person, mostly their character, is attacked
even someone of poor character can produce a good argument
o Abusive Ad Hominem (Mudslinging)
Opponent is insulted or abused (attacks person)
Very effective because no one will trust the
attacked
o Circumstantial ad Hominem (Vested Interest)
Accusing opponent of a biased argument
Arguing that opponent has something to gain
from their own argument
Focuses on their circumstance or situation
o Guilt by Association
Opponents argument is discredited for being part of a
particular group
o Tu Quoque
Charge of hypocrisy
Accusing someone of not practicing what they preach
Focusing on opponents behaviour
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