Logic: Chapter Three: Sections III

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Logic Chapter Three Sections III

• Jay Odenbaugh
• Philosophy
• Lewis and Clark College

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Inductive Arguments

• An argument is inductive if the conclusion is
  probably when the premises are true.
• Thus, IA are invalid it is possible for the
  premises to be true and the conclusion false.
• Inductive arguments are amplitative the
  conclusion contains information not contained in
  the premises.
• .

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Varieties of Inductive Arguments Causal
Arguments

• Causal claim
• Effect claim
• Correlational premises
• Causal claim
• For example,
• There is a strong correlation between smoking and
  lung cancer. Probably, smoking causes lung cancer.

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Varieties of Inductive Arguments Past-Future
Arguments

• Past claims
• Future claims
• For example,
• A presidential candidate has not won the
  presidency with out carrying some of the Southern
  states in the past.
• Probably, no future candidate can do so either.

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Varieties of Inductive Argument
Present-to-Future/Present-to-Past Arguments

• Present claims
• Future claims
• Present claims
• Past claims
• For example,
• Since Sadam Hussein did not have weapons of
  mass destruction now, it is unlikely that he did
  in the past.

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Varieties of Inductive Arguments Sample to
Population

• Sample claims
• Population claims
• For example,
• Most Oregonians polled are against Measure 36.
  Probably, all Oregonians are against Measure 36.

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Varieties of Inductive Arguments Particular Case
Based on a Generalization

• Generalization
• Particular Case
• For example,
• Usually, the Grammy Awards are a waste of time.
• The Grammy Awards this evening will be a waste
  of time.

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Varieties of Inductive Arguments Analogy

• Similarity
• Object1(s)
• Object2(s)
• For example,
• Amy and Jon both like a lot of the same music.
• Probably, they will both like the White Stripes.

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Indicator Words

• Indicator words probably, usually, tends to
  support, likely, very likely, almost always
• Weak may, might, possibly
• Strong almost always, highly improbable, very
  likely
• Some terms can be used in inductive and deductive
  arguments beyond all reasonable doubt

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Additional Premises

• Inductive arguments can change in strength with
  the addition of premises deductive arguments
  cannot.
• Since Sadam Hussein did not have weapons of mass
  destruction now though he did somehow gassed the
  Kurds in past, it is unlikely that he did in the
  past.