BASIC CONCEPTS OF ARGUMENTS

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BASIC CONCEPTS OF ARGUMENTS
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What is an Argument?

• To justify or defend a claim is to give reasons
  or arguments to support it.
• Reasoning (or inference) is a psychological
  process.
• When we express this process into words, we have
  arguments.
• An argument is set of STATEMENTS (or
  propositions) composed of PREMISES and
  CONCLUSION such that the former supports the
  latter.

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What is an Argument?

• A STATEMENT is a sentence that is either T or F.
• So questions, commands, requests are not
  statements.

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What is an Argument?

• The structure of an argument
• Premise 1
• Premise 2
• Premise 3
• Premise n
• -----------------
• Conclusion

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What is an Argument?

• Example of argument
• Cats are mammals.
• Mammals are animals.
• ---------------------------------
• Therefore, cats are animals.

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What is an Argument?

• Example of argument
• Most people who are infected with HIV will
  develop AIDS.
• He is infected with HIV.
• -------------------------------------------------
  -------
• He will develop AIDS.
•  

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What is an Argument?

• Conclusion indicators therefore, hence, thus,
  so, as a result, wherefore . .
• Premise indicators since, for , because, as,
  given that, owing to . . .

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What is an Argument?

• SUB-CONCLUSION
• Sometimes, one or more of the premises of an
  argument support a conclusion as a statement that
  in itself serves as a premise in the argument for
  the final conclusion. Such a statement is a
  sub-conclusion of the argument.

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What is an Argument?

• E.g.
• 1. Leon is a handsome man. (premise)
• 2. Handsome men are admired by many. (premise)
• 3. Therefore, Leon is admired by many.
  (sub-conclusion)
• 4. No one admires a drug addict. (premise)
• 5. Therefore, Leon is not a drug addict.
  (conclusion)

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What is an Argument?

• IMPLICIT (OR UNSTATED) PREMISE
• An implicit premise of an argument is a statement
  that is assumed but needs to be added to the
  premises if they are to support the conclusion.

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What is an Argument?

• E.g. What is the implicit premise in the
  following argument?
• 1. All murder is immoral.
• 2. Therefore, mercy killing is immoral.

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What is an Argument?

• E.g. What is the implicit premise in the
  following argument?
• 1. Smoking is bad to health.
• 2. Therefore, you should quit smoking.

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Passages Similar to Arguments

• EXPLANATIONS
• They have the same structure of arguments but the
  reasons given in an explanation are not used to
  prove a claim. Instead, they are used to make
  sense of a claim that has already been well
  accepted.
• E.g., "smoking is bad to health because it will
  cause lung cancer."

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Passages Similar to Arguments

• Conditional propositions
• They state that something will happen if certain
  conditions are fulfilled.
• E.g., "if you work hard, you will pass the test."

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Passages Similar to Arguments

• Statements of belief
• They simply express someone's beliefs without
  providing any evidence to support those beliefs.
• E.g., "I believe that he is guilty and should be
  put to jail."

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The Logical Strength of an Argument

• The logical strength of an argument is the
  measure of how its premises, assumed to be true,
  support its conclusion.
• We divide arguments into two types according to
  their logical strength
• Deductive arguments
• Inductive arguments

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The Logical Strength of an Argument

• Deductive argument
• If all its premises are true, its conclusion is
  logically impossible to be false.
• I.e. The truth of its premises guarantees the
  truth of its conclusion.
• E.g. All cats are mammals, and all mammals are
  animals. Therefore, all cats are animals.

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The Logical Strength of an Argument

• Inductive argument
• If all its premises are true, its conclusion is
  likely to be true but still possible to be false.
• I.e. The truth of its premises makes it
  reasonable to hold that the conclusion is true.
• E.g. Most people who are infected with HIV will
  develop AIDS. And he is infected with HIV.
  Therefore, he will develop AIDS.