Reconstructing Arguments

1
Reconstructing Arguments

• Chapter 4

2
Reconstruction

• In real life arguments do not come with the
  premises and conclusions neatly labeled.
• Reconstruction Two phases
• identifying the premises and conclusions
• Identifying the structure of the argument

3
Reconstruction

• Conventions
• The conclusion is underlined and represented by C
• Premises are enclosed in brackets and represented
  by P1, P2, P3,
• A missing premise or conclusion is represented by
  MPx or MC.

4

• The most important challenge facing educators
  today is to teach students how to write decent
  prose. By decent prose I do not mean elegant
  writing I mean simple straightforward writing
  that conforms to the rules of English grammar and
  clearly conveys its meaning. The ability to
  write decent prose is important because those who
  lack it will be unable to understand the great
  achievements of our cultural heritagewhether of
  Homer or Hemingwayand, perhaps even more
  important, will be unable to communicate
  effectively in todays world.

5

• The most important challenge facing educators
  today is to teach students how to write decent
  prose (C). By decent prose I do not mean
  elegant writing I mean simple straightforward
  writing that conforms to the rules of English
  grammar and clearly conveys its meaning. The
  ability to write decent prose is important
  because those who lack it will be unable to
  understand the great achievements of our cultural
  heritagewhether of Homer or Hemingwayand,
  perhaps even more important, will be unable to
  communicate effectively in todays world.

6

• The most important challenge facing educators
  today is to teach students how to write decent
  prose (C). By decent prose I do not mean
  elegant writing I mean simple straightforward
  writing that conforms to the rules of English
  grammar and clearly conveys its meaning. The
  ability to write decent prose is important
  because those who lack it will be unable to
  understand the great achievements of our cultural
  heritagewhether of Homer or Hemingway (P1)and,
  perhaps even more important, will be unable to
  communicate effectively in todays world.

7

• The most important challenge facing educators
  today is to teach students how to write decent
  prose (C). By decent prose I do not mean
  elegant writing I mean simple straightforward
  writing that conforms to the rules of English
  grammar and clearly conveys its meaning. The
  ability to write decent prose is important
  because those who lack it will be unable to
  understand the great achievements of our cultural
  heritagewhether of Homer or Hemingway (P1)and,
  perhaps even more important, will be unable to
  communicate effectively in todays world (P2).

8

• P1 Those who lack the ability to write decent
  prose will be unable to understand the great
  achievements of our cultural heritagewhether of
  Homer or Hemingway.
• P2 Those who lack the ability to write decent
  prose will be unable to communicate effectively
  in todays world.
• C The most important challenge facing educators
  today is to teach students how to write decent
  prose.

9
Missing Premises and Conclusions

• In many real life arguments, some premises, and
  sometimes, even the conclusion, are left out.
• Without those premises and conclusions, the
  arguments are quite weak.
• Therefore, according to our principle of charity,
  we ought to include them in a reconstruction of
  that argument.

10
Missing Premises and Conclusions

• P1 Dougs birthday is tomorrow
• C Therefore Bob should buy him a present.
• Is this a good argument?
• As it stands, no. But assuming the speaker is
  rational, we need to fix it so that it is good.

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Missing Premises and Conclusions

• P1 Dougs birthday is tomorrow
• MP2 Bob is Dougs brother
  .
• C Therefore Bob should buy him a present.
• Is it now a good argument?
• Well, its better.

12
Missing Premises and Conclusions

• P1 Dougs birthday is tomorrow
• MP2 Bob is Dougs brother
• MP3 Siblings ought to buy each other presents on
  their birthdays .
• C Therefore Bob should buy him a present.

13
Missing Premises and Conclusions

• P1 High crime rates are caused by the widespread
  use of probation and suspended sentences.
• C Therefore, we should amend the criminal law to
  provide for mandatory minimum prison sentences
  for all crimes.
• Good argument?
• As it stands NO!

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Missing Premises and Conclusions

• P1 High crime rates are caused by the widespread
  use of probation and suspended sentences.
• MP2 There are high crime rates.
• MP3 Mandatory minimum prison sentences for all
  crimes will decrease crime rates.
• C Therefore, we should amend the criminal law to
  provide for mandatory minimum prison sentences
  for all crimes.

15
Missing Premises and Conclusions

• Missing premises can be either
• Factual facts about the world which, if true,
  would increase the strength of the argument.
• E.g., There are high crime rates
• E.g., Bob is Dougs brother
• Presuppositions general principles assumed to
  true, which explains why the speaker believes the
  premises support the conclusion
• E.g., Mandatory minimum prison sentences for all
  crimes will decrease crime rates.
• E.g., Siblings ought to buy each other presents
  on their birthdays

16
Self test No. 8

• 2. Whenever your cars engine is flooded, you
  should put the accelerator right to the floor and
  then try to start it. So floor it and try again.

17
Self test No. 8

• 2. Whenever your cars engine is flooded, you
  should put the accelerator right to the floor and
  then try to start it (P1). So floor it and try
  again (C).
• P1 Whenever your cars engine is flooded, you
  should put the accelerator right to the floor and
  then try to start it.
• C Floor it and try again

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Self test No. 8

• P1 Whenever your cars engine is flooded, you
  should put the accelerator right to the floor and
  then try to start it.
• C Floor it and try again
• Whats missing?
• MP2 The cars engine is flooded.

19
Self test No. 8

• 3. But you are still a Catholic, and Catholics
  are supposed to make a special efforts to attend
  church at Easter.

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Self test No. 8

• 3. But you are still a Catholic (P1), and
  Catholics are supposed to make a special efforts
  to attend church at Easter (P2).
• P1 You are still a Catholic
• P2 Catholics are supposed to make a special
  efforts to attend church at Easter.

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Self test No. 8

• P1 You are still a Catholic
• P2 Catholics are supposed to make a special
  efforts to attend church at Easter.
• Whats missing?
• MC You ought to make a special effort to attend
  church at Easter.

22
Self test No. 8

• 10. There ought to be a law prohibiting the use
  of animals in research. After all, we would not
  tolerate that kind of treatment of humans.

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Self test No. 8

• 10. There ought to be a law prohibiting the use
  of animals in research (C). After all, we would
  not tolerate that kind of treatment of humans
  (P1).
• P1 We would not tolerate that kind of treatment
  of humans.
• C There ought to be a law prohibiting the use of
  animals in research.

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Self test No. 8

• P1 We would not tolerate that kind of treatment
  of humans.
• C There ought to be a law prohibiting the use of
  animals in research.
• Whats missing?
• MP2 Other animals ought to be treated the same
  as humans, and deserve the same sort of legal
  protection.

25
Special Cases

• Not everything that contains premises and a
  conclusion is an argument.
• Reports of arguments
• Explanations

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Special Cases

• Reports of Arguments
• In these cases what we have is a description of
  an argument.
• A description of an argument is not an argument,
  even though the description itself contains
  premises and conclusions.

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Special Cases

• Reports of Arguments
• E.g.
• John refuses to vote in elections because he
  believes that all politicians are dishonest.
• This is a description of an argument that John
  thinks is sound.
• Descriptions are either true or false. This
  description is true if this is what John actually
  believes.

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Special Cases

• Explanations
• Explanations attempt to show how or why something
  happened.
• Again, even though there are premises and
  conclusions here, explanations are not arguments.
• Explanations attempt to give reasons for or
  causes why something happened. They are not
  attempts to persuade you of anything.

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Special Cases

• Explanations
• E.g.
• The Canadiens got a penalty because they had too
  many people on the ice.
• In this case, it is clear that getting a penalty
  follows from the fact that they had too many
  people on the ice, but the force of follows
  from here is not inferential, but rather causal.

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Self-test No. 9
31
The Structure of Arguments

• The structure of an argument tells us how the
  premises are intended to support the conclusion.
• The easiest way to see the structure of an
  argument is through a tree diagram.
• A tree diagram is a schematic representation of
  the structure of an argument, using the letters
  P1, P2, , MP1, MP2, , C, MC, and ? to represent
  therefore.

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The Structure of Arguments

• Simple arguments
• Simplest argument has one premise.
• P1 When Jim quit playing the trumpet, he gave it
  to his younger brother.
• C Hence, Jim wont be able to lend his trumpet
  to Andrew.

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Simple Arguments

• P1
• C

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Arguments with more than one premise

• If an argument is not a simple argument, if it
  contains more than one premise, then there are
  two possible structures the argument might have.
• We call these
• T arguments
• V arguments

35
T arguments

• In T arguments, the premises, when taken by
  themselves, provide little or no support for the
  conclusion.
• It is only when all the premises are taken
  together that the argument is regarded as having
  logical strength.
• In the diagram, the lines joining the premises to
  the conclusion form a T.

36
T Arguments

• P1 Every medical doctor has to tell someone that
  a loved one has died.
• P2 Beth is a medical doctor.
• C Therefore, Beth has to tell someone that a
  loved one has died.
• P1 P2
• C

37
V Arguments

• In V arguments, the premises are regarded as
  independent reasons for thinking the conclusion
  is true.
• If one premise is missing or false, the other
  premises still provide support for the
  conclusion.
• In the diagram, the lines joining the premises to
  the conclusion form a V (there are no lines
  joining the premises).

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V Arguments

• P1 Frances is very successful in her career.
• P2 Frances has a secure and supportive marriage.
• P3 Frances had a stable and secure childhood.
• C Therefore Frances is a happy person.
• P1 P2 P3
• C

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Complex Arguments

• Premises which are sub-conclusions
• In some complex arguments, there are actually
  going to be two or more conclusions, where some
  of those conclusions will in turn be used as
  premises to support the main conclusion.

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Premises which are sub-conclusions

• E.g.
• P1 Max was born in Canada
• P2 That means Max is a Canadian citizen
• C Therefore, Max can vote in federal elections
• This argument consists of two subarguments.

41
Premises which are sub-conclusions

• P1 Max was born in Canada
• P2 That means Max is a Canadian citizen
• C Therefore, Max can vote in federal elections
• P1
• P2
• C

42
Complex Arguments

• Complex arguments which contain some of or all
  simple arguments, T arguments and/or V arguments.
• When examining the premises, it could be the case
  that some will be sub-conclusions from other
  premises, some will only support the conclusion
  if other premises are true, and that yet others
  will offer independent support for the conclusion.

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E.g. pp. 99-100

• P1 When the Meech Lake agreement was negotiated,
  it had the support of the Prime Minister and all
  provincial premiers, who represented all the
  major political parties.
• P2 In several provinces the opposition parties
  voted to ratify the agreement.
• P3 So politicians of all political parties
  across Canada strongly supported the agreement.
• P4 However, the vast majority of Canadians
  outside Quebec, and a significant minority inside
  Quebec were strongly opposed to the agreement.
• C Therefore the politicians were out of touch
  with the views of the people.

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• P1 P2
• P3 P4
• C

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Self-Test No. 10
46

• Anyone who has brains and ambition will go far in
  this world. Carla certainly has got both, so she
  will go far.
• Anyone who has brains and ambition will go far
  in this world (P1). Carla certainly has got
  both (P2), so she will go far (C).

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• P1 Anyone who has brains and ambition will go
  far in this world.
• P2 Carla certainly has got both brains and
  ambition
• C Carla will go far.
• P1 P2
• C

48

• 3. The Expos should win the National League
  pennant this year. They have solid depth in
  their pitching staff, their hitting has been
  consistently good this year, their coaching is
  excellent, and there is good team spirit.
• The Expos should win the National League pennant
  this year (C). They have solid depth in their
  pitching staff (P1), their hitting has been
  consistently good this year (P2), their
  coaching is excellent (P3), and there is good
  team spirit (P4).

49

• The Expos should win the National League pennant
  this year (C). They have solid depth in their
  pitching staff (P1), their hitting has been
  consistently good this year (P2), their
  coaching is excellent (P3), and there is good
  team spirit (P4).
• P1 The Expos have solid depth in their pitching
  staff
• P2 Their hitting has been consistently good this
  year
• P3 Their coaching is excellent
• P4 There is good team spirit
• C The Expos should win the National League
  pennant this year.

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• P2 P3
• P1 P4
• C