Arguments in Philosophy

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Arguments in Philosophy

• Introduction to Philosophy

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Arguments

• Philosophy is the art of constructing and
  evaluating arguments
• Its all about the argument
• Arguments are meant to be convincing
• So philosophers must be sensitive to what makes
  an argument convincing
• Or not

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Thinking Critically

• First step Think Critically
• What is the argument trying to say?
• Why does the argument succeed, or not?
• Whats good, bad, or indifferent?
• The form of the argument
• Whats the point?
• How do we get to the point?
• Structure
• How do the parts of the argument fit together?

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General Structure

• In general, arguments consist of
• The thesis or position argued for
• The conclusion
• The reasons why the conclusion should be accepted
• The premises
• Usually this is written in standard form

Premise 1 (Justification) Premise 2
(Justification) Therefore, Conclusion
(Justification)
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Two kinds of argument

• In general, there are two kinds of argument
• Deductive Arguments
• Inductive Arguments
• These arguments work (slightly) differently, so
  theyre evaluated differently

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But lets be more specific

• A statement is any unambiguous declarative
  sentence about a fact (or non-fact) about the
  world.
• It says that something is (or isnt) the case.
• An argument is a series of statements meant to
  establish a claim.
• A claim or conclusion is the statement whose
  truth an argument is meant to establish.
• A statements truth value is either true or
  false.
• All statements have a truth value. A statement
  is false when what it says about the world is not
  actually the case. A statement is true when what
  it says about the world is actually the case.
• A premise is a statement that is used in an
  argument to establish a conclusion.

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Deductive Arguments

• A deductive argument is
• VALID if its premises necessarily lead to its
  conclusion.
• That is, if you were to accept that the premises
  are all true, you must accept that the conclusion
  is true.
• SOUND if it is valid and you accept that all its
  premises are true.
• A good, convincing argument is sound.
• A bad argument is any other kind of argument.
• VALIDITY TRUE PREMISES SOUND
• or, at least, accepted premises

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Examples

• All people are mortal. Socrates is a person.
  Therefore, Socrates is mortal.
• Sound
• All people are mortal. My dog is mortal.
  Therefore, my dog is a person.
• Invalid.
• Oranges are green. All green things make me
  sick. Therefore, oranges make me sick.
• Valid. Not sound.
• Whales know how to play hockey. Therefore,
  Canadians like winter.
• Invalid.

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Notice

• Validity does not depend on the truth of the
  premises.
• All people are mortal. My dog is mortal.
  Therefore, my dog is a person.
• The premises are true. But the argument is still
  invalid.
• Soundness does not depend on the truth of the
  conclusion.
• An argument can be bad even if the conclusion is
  obviously true.

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Evaluating Deductive Arguments

• Good arguments must be sound.
• If you want to accept of an argument, you would
  have to show both validity and soundness
• Bad arguments can be bad in two ways
• Invalid
• You can show that the conclusion does not follow
  from the premises
• Unsound
• You can show that at least one premise is
  unacceptable

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Inductive Arguments

• Inductive arguments are not truth preserving
• Even in a good inductive argument where the
  premises are true, the conclusion does not have
  to be true.
• At most, the conclusion is most likely true.
• Inductive arguments are meant to make conclusions
  more likely or more acceptable.

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Inductive Arguments

• An inductive argument is
• STRONG if its premises make the conclusion
  probable
• That is, if you were to accept the premises as
  true, then you would have to accept that the
  conclusion was probably true
• COGENT if it is strong and its premises are
  accepted
• A good, convincing argument is cogent.
• STRENGTH TRUE PREMISES COGENT

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Examples

• This cooler contains 30 cans. 25 cans selected
  at random contained soda. Therefore, all the
  cans probably contain soda.
• Cogent
• This cooler contains 30 cans. 3 cans selected at
  random contained soda. Therefore, all the cans
  probably contain soda.
• Weak
• Every monkey Ive seen (over 500) has blue teeth.
  Therefore, the next monkey I see will probably
  have blue teeth.
• Strong, but not cogent

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Notice

• Strength admits of degrees.
• An argument can be stronger or weaker
• Usually, the more evidence available, the
  stronger the argument
• Strength does not depend on the truth of the
  premises

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Evaluating Inductive Arguments

• Good arguments must be cogent.
• If you want to accept of an argument, you would
  have to show both strength and cogency
• Bad arguments can be bad in two ways
• Weak
• You can show that the premises does not make the
  conclusion more probable
• Not cogent
• You can show that at least one premise is
  unacceptable

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Argument by Analogy

• One particular kind of inductive argument is an
  Argument by Analogy
• Comparison of two or more things
• Concludes that they share characteristic(s)
• Because they share other characteristic(s)
• Example
• Watches exhibit order, function, and design.
  They were also created by a creator. The
  universe exhibits order, function, and design.
  Therefore, the universe probably was created by a
  creator.
• Evaluated like other inductive arguments

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In Practice

• Identify the conclusion
• What is the claim?
• Identify the premises
• How is the claim supported?
• Often, we first have to get rid of anything
  unnecessary mere rhetorical flourishes,
  repetitions, and irrelevancies.
• Reformulate the argument
• Try to put it into standard form
• Often, well have to add premises that are
  implied but not stated.

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In Practice

• Identify the form of the argument
• How are the premises supposed to lead to the
  conclusion?
• Deductive? Inductive?
• Assumptions? Subarguments?
• (This will help us add/delete premises)
• Evaluate the argument
• Valid? Sound?
• Strong? Cogent?
• WHY?

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Example

• For Death is to be as it were nothing, and to be
  deprived of all sensation... And if no sensation
  remains, then death is like a dreamless sleep.
  In this case, death will be a blessing. For, if
  any one compares such a night as this, in which
  he so profoundly sleeps as not even to see a
  dream, with the other nights and days of his
  life, and should declare how many he had passed
  better and more pleasantly than this night, I
  think that not only a private man, but even the
  great king himself, would find so small a number
  that they might be easily counted.

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Example

• For Death is to be deprived of all sensation...
  if no sensation remains, then death is like a
  dreamless sleep. ...death will be a blessing.
  ...if any one compares such a night of sleep
  without dreams... with the other nights and days
  of his life, and should declare how many he had
  passed better and more pleasantly than this
  night, I think.. he would find so small a
  number...

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Example

• Death is to be deprived of all sensation.
• If no sensation remains, death is like a
  dreamless sleep.
• Anyone will consider a dreamless sleep better
  than most days and nights.
• ---
• Death is a blessing.

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Example

• Death is to be deprived of all sensation.
• If no sensation remains, death is like a
  dreamless sleep.
• Death is like a dreamless sleep.
• Anyone will consider a dreamless sleep better
  than most days and nights.
• Anyone will consider death better than most days
  and nights.
• Anything that is better than most days and nights
  is a blessing.
• ---
• Death is a blessing.

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Example

• Death is to be deprived of all sensation.
  (Assumption)
• If no sensation remains, death is like a
  dreamless sleep. (Assumption)
• Death is like a dreamless sleep. (Conclusion from
  1 and 2)
• Anyone will consider a dreamless sleep better
  than most days and nights. (Assumption)
• Anyone will consider death better than most days
  and nights. (Conclusion from 3 and 4)
• Anything that is better than most days and nights
  is a blessing. (Assumption)
• ---
• Death is a blessing. (From 3, 5, and 6)