Analyzing Arguments

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Lecture 9

• Analyzing Arguments
• Diagramming Short Arguments

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• This is a bit of historical documentation of what
  Spring Breaks were like when I was an
  undergraduate (well, really when I was still in
  high school) .
• Welcome Back from Spring Break

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Today Analyzing ArgumentsBut first, a fallacy
in the news

• Can you spot it? What kind of fallacy is this?
• What Obama said re. Trayvon Martin
• What Gingrich said Obama said re. Trayvon Martin

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Arguments Review

• Arguments consist of premises and conclusions.
• Premises and conclusions are statements.

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Arguments Review

• Premise indicator words since, because, for,
  given that, seeing that, considering that,
  inasmuch as, as, in view of the fact that, as
  indicated by, judging from, on account of
• Conclusion indicator words therefore, thus,
  hence, consequently, so, accordingly, it follows
  that, for this reason, that is why, which shows
  that, wherefore, this implies that, as a result,
  this suggests that, this being so, we may infer
  that.

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Diagramming Short Arguments

• Argument
• The death penalty should be abolished because
  its racially discriminatory, theres no evidence
  that its a more effective deterrent than life
  imprisonment, and innocent people may be executed
  by mistake.

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Diagramming Short Arguments

• Step 1 Identify (circle, underline, etc.) all
  premise and / or conclusion indicators.
• The death penalty should be abolished because
  its racially discriminatory, theres no evidence
  that its a more effective deterrent than life
  imprisonment, and innocent people may be executed
  by mistake.

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Diagramming Short Arguments

• Step 2 Number the statements consecutively as
  they appear in the argument.
• The death penalty should be abolished
• because its racially discriminatory,
• theres no evidence that its a more effective
  deterrent than life imprisonment, and
• innocent people may be executed by mistake.

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Diagramming Short Arguments

• Step 3 Arrange the numbers on a page with the
  premises placed above the conclusion(s) they
  claim to support.
• 2) 3) 4)
• 1)

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Diagramming Short Arguments

• Step 4 Omit any logically irrelevant
  statements.
• Step 5 Use arrows to mean is offered as
  evidence for to show relationship of argument
  support.
• 2) 3) 4)
• 1)
• Here 2), 3), and 4) offer independent support for
  the conclusion.

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Diagramming Short Arguments

• A premise provides independent support for a
  conclusion when the amount of support it provides
  would not be weakened or destroyed by the removal
  of any other premise in the argument.
• A premise provides linked support when it works
  conjointly with another premise to support the
  conclusion
• EXAMPLE No member of the SJSU community is a
  fan of the Leland Stanford Junior University
  Marching Band. Maurice is a member of the SJSU
  community. So, Maurice is not a fan of the Leland
  Stanford Junior University Marching Band.

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Diagramming Short Arguments Linked Support

1. No members of the SJSU community is a fan of the
   Leland Stanford Junior University Marching Band.
2. Maurice is a member of SJSU community.
3. So, Maurice is not a fan of the Leland Stanford
   Junior University Marching Band.

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Diagramming Short Arguments

• Linked Support
• 1) 2)
• 3)

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Linked or Independent Support?

• Linked Omission of one premise cancels / reduces
  support provided by the other.
• Example
• No student in Ling 21 is a Rhodes Scholar.
• Josue is a Rhodes Scholar.
• So, Josue is not a student in Ling 21.

• Independent Neither premise would provide less
  support for the conclusion if the other were
  omitted.
• Example
• Nick doesnt own a car. Nick is legally blind.
• So Nick probably wont drive a car to the game.

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Linked or Independent Support?

• Ten witnesses say they saw Blotto rob the bank.
  The stolen bank money was found in Blottos car.
  Blottos fingerprints were found at the Tellers
  window. Therefore, Blotto probably robbed the
  bank.
• If Amy runs marathons, then shes probably very
  fit. Amy does run marathons. So Amy probably is
  very fit.

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Other Kinds of Support

• Jim is a senior citizen.
• So, Jim probably doesnt like hip-hop music.
• So, Jim probably wont be going to the Ashanti
  concert tonight.
• 1)
• 2)
• 3)

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Other Kinds of Support

• Example
• Most Democrats are liberals, and Senator
  Dumdiddle is a Democrat. Thus, Senator Dumdidle
  is probably a liberal. Therefore, Senator
  Dumdiddle probably supports affirmative action in
  higher education, because most liberals support
  affirmative action in higher education.

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Other Kinds of Support

• Example
• Most Democrats are liberals, and
• Senator Dumdiddle is a Democrat.
• Thus, Senator Dumdidle is probably a liberal.
• Therefore, Senator Dumdiddle probably supports
  affirmative action in higher education,
• because most liberals support affirmative action
  in higher education.

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Other Kinds of Support

• Premises and conclusions
• 1) 2)
• 3) 5)
• 4)

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Other Kinds of Support

• Cheating is wrong for several reasons. First, it
  will lower your self-respect, because you can
  never be proud of anything you got by cheating.
  Second, cheating is a lie because it deceives
  other people into thinking you know more than you
  do. Third, cheating violates the teachers trust
  that you will do your own work. Fourth, cheating
  is unfair to all the people who arent cheating.
  Finally, if you cheat in school now, youll find
  it easier to cheat in other situations later in
  life perhaps even in your closest personal
  relationships.

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Other Kinds of Support

• 1) Cheating is wrong for several reasons.
• 2) First, it will lower your self-respect,
• 3) because you can never be proud of anything you
  got by cheating.
• 4) Second, cheating is a lie
• 5) because it deceives other people into thinking
  you know more than you do.
• 6) Third, cheating violates the teachers trust
  that you will do your own work.
• 7) Fourth, cheating is unfair to all the people
  who arent cheating.
• 8) Finally, if you cheat in school now, youll
  find it easier to cheat in other situations later
  in life perhaps even in your closest personal
  relationships.

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Other Kinds of Support

• Notice the use of because in 3) and 5)
• 3) 5)
• 2) 4)

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Other Kinds of Support

• Note that 2), 4), 6), 7), and 8) all provide
  independent support for the main conclusion 1)
• 3) 5)
• 2) 4) 6) 7) 8)
• 1)

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Tips on Diagramming Short Arguments

• Find the main conclusion first
• Pay close attention to premise and conclusion
  indicators.
• Remember sentences containing the word and
  often contain two or more separate statements.
• Treat conditional statements (if-then) and
  disjunctive statements (either-or) as single
  statements.
• Dont number / diagram any sentence that is not a
  statement.
• Dont diagram irrelevant statements.
• Dont diagram redundant statements.

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Practice

• Critical Thinking, p. 171-75, Exercise 7.1
• Step 1 Identify (circle, underline, etc.) all
  premise and / or conclusion indicators.
• Step 2 Number the statements consecutively as
  they appear in the argument.
• Step 3 Arrange the numbers on a page with the
  premises placed above the conclusion(s) they
  claim to support.
• Step 4 Omit any logically irrelevant
  statements.
• Step 5 Use arrows to mean is offered as
  evidence for to show relationship of argument
  support.