Evaluating moral arguments

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Chapter 3

• Evaluating moral arguments

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REVIEW

• Last time, we discussed subjective relativism,
  cultural relativism, emotivism, and ethical
  objectivism.
• We considered arguments for and against each
  view.
• While ethical objectivism is the theory that best
  accords with most intuitive conceptions of
  morality, many thinkers have suggested
  interesting reasons to embrace alternate views.

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REVIEW

• If someone were to betray your trust or to
  physically injure you for no other reason than
  his/her own pleasure, you might think that person
  has done something wrong.
• Yet, if the agent who has acted against you, acts
  in accordance with his/her personal views or
  those of his/her particular culture, a relativist
  could argue that the agents actions were
  justified and it was morally permissible for him
  to hurt you.

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REVIEW

• A moral skeptic or an emotivist might argue that
  there is no such thing as a morally impermissible
  action and that when one says that an action is
  morally wrong, s/he isnt making any claim at
  all, but rather something else is going on.

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REVIEW

• An ethical objectivist would use some objective
  criteria to evaluate an action. S/he might argue,
  for instance, that any time someone harms another
  for no other reason than his/her own pleasure,
  the agent performs an act that is morally wrong.
• In order to determine and evaluate such criteria,
  one needs to apply critical reasoning.

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WHAT IS MORAL REASONING?

• Moral reasoning is ordinary critical reasoning
  applied to moral arguments.
• Critical reasoning (also called critical
  thinking) is the careful, systematic evaluation
  of statements and arguments.

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STATEMENTS

• A statement (or claim) is the assertion that
  something is either true or false. The following
  are all statements
• Murder is wrong
• 1 1 2
• Shakespeare wrote The Tempest

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ARGUMENTS

• When at least one statement attempts to provide
  reasons for believing another statement, we have
  an argument--a group of statements, one of which
  is supposed to be supported by the rest.

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Statements and Arguments

• The statement that is being supported by the
  others is the conclusion.
• The supporting statements are called premises.

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IDENTIFYING ARGUMENTS

• An argument has something to prove.
• The most reliable way to identify arguments is to
  look for the conclusion first.
• Next, establish that there is a connection
  linking premises to the conclusion.
• A cluster of unrelated claims is not an argument.

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ARGUMENT OR NOT?

• The number of abortions performed in this state
  is increasing. More and more women say that they
  favor greater access to abortion. I disapprove
  of abortion.
• This is NOT an argument. There is no clear
  connection among its statements.

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ARGUMENT OR NOT?

• The number of abortions performed in this state
  is increasing. More and more women say that they
  favor greater access to abortion. Clearly, the
  trend among women in this state is toward greater
  acceptance of abortion.
• This IS an argument. There is a clear
  conclusion that is supported by the other
  statements in the paragraph.

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Two Forms of Argument

• A deductive argument is supposed to give
  logically conclusive support to its conclusion.
• An inductive argument is supposed to offer
  probable support to its conclusion.

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Deductive Arguments

• The following deductive argument is valid
• If its premises are true, then its conclusion
• must be true
• All human beings are mortal.
• Socrates is a human being.
• Therefore, Socrates is mortal.
• A valid argument with true premises (such as
• the example above) is said to be sound.

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Deductive Arguments

• An invalid deductive argument is an argument in
  which the premises do not offer conclusive
  support for its conclusion
• All ducks are mortal.
• Socrates is a human being.
• Therefore, Socrates is mortal.
• Validity and invalidity are matters of form,
• not content, of an argument.

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Common Deductive Argument Forms

• VALID FORMS
• Affirming the antecedent
• Denying the consequent
• The hypothetical syllogism
• INVALID FORMS
• Denying the antecedent
• Affirming the consequent

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Affirming the Antecedent

• Takes the form
• If p, then q.
• p.______
• Therefore, q.
• This form is always valid if the premises are
• true, then the conclusion has to be true.

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Denying the Consequent

• Takes the form
• If p, then q.
• Not q._______
• Therefore, not p.
• This form is always valid if the premises
• are true, then the conclusion has to be true.

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The Hypothetical Syllogism

• Takes the form
• If p, then q.
• If q, then r.
• Therefore, if p, then r.
• This form is always valid if the premises
• are true, then the conclusion has to be true.

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Denying the Antecedent

• Takes the form
• If p, then q.
• Not p_______
• Therefore, not q.
• This form is always invalid the
• conclusion can be false even if the premises
• are true.

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Affirming the Consequent

• Takes the form
• If p, then q.
• q.________
• Therefore, p.
• This form is always invalid the
• conclusion can be false even if the premises
• are true.

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Strong Inductive Arguments

• The following inductive argument is strong it
  gives probable support to its conclusion such
  that, if its premise is true, its conclusion is
  also likely to be true
• Ninety percent of men at this college have
  combined SAT scores over 1400. Therefore, Julio
  (a student at this college) probably has a
  combined SAT score over 1400.
• A strong inductive argument with true premises is
  said to be cogent.

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Weak Inductive Arguments

• The following inductive argument is weak it does
  not give probable support to its conclusion, and
  even if its premise is true, its conclusion is
  not more likely to be true
• Ten percent of the men at this college have
  combined SAT scores over 1400. Therefore, Julio
  (a student at this college) probably has a
  combined SAT score over 1400.

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Practice Questions

• Which of the following are arguments?
• I like puppies. They are wonderful and playful.
  Sometimes they eat apples. I like apples too.
• We should stop testing cosmetics on puppies. They
  are animals, and non-human animals have rights
  just like human beings do.
• Everyone who likes puppies should get in A in
  this course. John likes puppies, so John should
  get an A.
• 4. Hooray, the Lions beat the Packers! I hate
  the Packers! Everyone knows that they are just
  terrible.

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Practice Questions

• Identify the Conclusion
• 1. John may have stolen that hundred dollar bill,
  but he was hungry and now, his financial troubles
  are over. Its unlikely that he will steal again,
  so John should not go to jail.
• If George W. Bush is a democrat, then all
  diamonds are purple. George W. Bush is a
  democrat. Therefore, all diamonds are purple.
• Its probable that the Earth is round, since most
  people believe the Earth is round.
• 4. As its going to rain, you shouldnt have
  your pool party today.

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Practice Questions

• Deductive or Inductive
• 1. John may have stolen that hundred dollar bill,
  but he was hungry and now, his financial troubles
  are over. Its unlikely that he will steal again,
  so John should not go to jail.
• If George W. Bush is a democrat, then all
  diamonds are purple. George W. Bush is a
  democrat. Therefore, all diamonds are purple.
• Most people believe the Earth is round, so its
  probable that the Earth is round.
• 4. Since its going to rain, you shouldnt have
  your pool party today.

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Practice Questions

• Valid or Invalid
• 1. All twiks are twoks. John is a twok.
  Therefore, John is a twik.
• If George W. Bush is a democrat, then all
  diamonds are purple. George W. Bush is a
  democrat. Therefore, all diamonds are purple.
• If Martha Custis was the first First Lady, then
  George Washington was the first U.S. president.
  George Washington was the first president.
  Therefore, Martha Custis was the first First
  Lady.
• 4. If John is your brother, then Tim is my
  cousin. If Tim is my cousin, then Eric is my
  uncle. Therefore, if John is your brother, then
  Eric is my uncle.

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Practice Questions

• Sound or Unsound
• 1. All U.S. presidents have been male. Gerald
  Ford was a U.S. president. Therefore, Gerald Ford
  must have been male.
• If George W. Bush is a democrat, then all
  diamonds are purple. George W. Bush is a
  democrat. Therefore, all diamonds are purple.
• No fish are mammals. Whales are fish. Therefore,
  whales are not mammals.
• 4. If grapes are oranges, then some oranges are
  of the genus Vitis. No oranges are part of the
  genus Vitis. Therefore, grapes are not oranges.