Introduction to Ethics Lecture 2 A deeper look at arguments - PowerPoint PPT Presentation

Loading...

PPT – Introduction to Ethics Lecture 2 A deeper look at arguments PowerPoint presentation | free to view - id: 6ebd3c-NTdjO



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Introduction to Ethics Lecture 2 A deeper look at arguments

Description:

Introduction to Ethics Lecture 2 A deeper look at arguments By David Kelsey Conclusions as premises Conclusions as premises: The Margaret example (example 1), 1 ... – PowerPoint PPT presentation

Number of Views:45
Avg rating:3.0/5.0
Slides: 20
Provided by: DavidK230
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Introduction to Ethics Lecture 2 A deeper look at arguments


1
Introduction to EthicsLecture 2A deeper look at
arguments
  • By David Kelsey

2
Conclusions as premises
  • Conclusions as premises
  • The Margaret example (example 1),
  • 1) Every student who made 90 percent or better on
    the midterms already has an A.
  • 2) Margaret made a 94 percent on the midterms.
  • Thus, 3) Margaret already has an A.
  • 1) Margaret already has an A.
  • 2) All students who have an A are excused from
    the final exam.
  • Thus, 3) Margaret is excused from the final exam.

3
Unstated Conclusions
  • Unstated Conclusions
  • Conclusions that are entailed by the words of the
    text.
  • The Republicans example (example 2)
  • 1) The political party that best reflects
    mainstream opinion will win the most seats in
    congress.
  • 2) The republicans certainly best reflect
    mainstream opinion.
  • What is the unstated conclusion?

4
IndependentPremises
  • Independent premises independently support the
    conclusion of an argument.

5
The speed limit example
  • An argument with independent premises
  • Speed limit example (example 3)
  • 1) Raising the speed limit will wear out the
    highways faster.
  • 2) Raising the speed limit will result in more
    highway deaths.
  • Thus, 3) We should not raise the speed limit.
  • 2 arguments

6
Dependent Premises
  • Dependent premises support the conclusion of an
    argument only with the help of some other
    premise.
  • Example Socrates is mortal
  • Question What if a dependent premise is false?

7
Good arguments
  • A good argument
  • The premises both support its conclusion and are
    reasonable
  • Reasonable?
  • Requisite Support?

8
Valid arguments
  • Valid arguments
  • Necessary connection between premises and
    conclusion
  • The premises entail the conclusion

9
Valid arguments false premises false
conclusions
  • We can have a valid argument with a false premise
    and a false conclusion.
  • George Bush example (example 5)
  • 1) George Bush is a robot.
  • 2) If George Bush is a robot then he isnt the
    president.
  • Thus, 3) George Bush isnt president.
  • And we can have a valid argument with false
    premises and a true conclusion
  • The moon is made of green cheese example (example
    6)
  • 1) The moon is made of green cheese.
  • 2) All things made of green cheese orbit the
    Earth.
  • Thus, 3) The moon orbits the Earth.

10
A validity metaphor
  • Form
  • Valid arguments have a certain form to them
  • The link between premises and conclusion
  • The puzzle metaphor

11
2 more Validity tricks
  • 2 more tricks
  • Addition metaphor
  • Imagine an argument as a mathematical problem of
    addition.
  • Covering up the conclusion
  • Cover up the conclusion and ask what do the
    premises entail?

12
Sound Arguments
  • A sound argument
  • The Superbowl example (example 7)
  • 1) The Ravens won the superbowl.
  • 2) If a team loses a playoff game, then they
    dont win the superbowl.
  • Thus, 3) The Ravens didnt lose a playoff game.
  • Dreaming example (example 8)
  • 1) Either I am in class right now or I am
    dreaming it.
  • 2) I am in class right now.
  • Thus, 3) I am not dreaming it.

13
Strong Arguments
  • A strong argument
  • April showers example (example 9)
  • 1) Every April we get some rain.
  • Thus, 2) We will get some rain this April.

14
Strong arguments false premises false
conclusions
  • A strong argument with a false premise and a
    false conclusion
  • Gravity example (example 10)
  • 1) Every time I have ever dropped anything from
    my hand it floats up to the sky.
  • Thus, 2) if I drop this pencil it will float up
    to the sky.
  • A strong argument with true premises and a false
    conclusion.
  • Swans example (11)
  • 1) Every swan I have ever seen is white.
  • Thus, 2) all swans are white.
  • (All swans are not in fact white as there are
    black swans in Australia!)

15
Cogent arguments
  • A cogent argument
  • 1.
  • 2.
  • The sun will rise set tomorrow (example 12)
  • 1) Every day of my life the sun has risen in the
    morning and set in the evening.
  • Thus, 2) Tomorrow the sun will rise in the
    morning and set in the evening.

16
Deduction and Induction
  • Deductive arguments
  • valid or intended to be valid.
  • Necessary conclusions
  • Conclusions built out of premises
  • Which of our 12 examples are deductive?
  • Inductive arguments
  • not valid.
  • Strong?
  • Likely conclusions
  • Prediction
  • Conclusion is new information
  • Which of our 12 examples are inductive?

17
Unstated Premises again
  • How to identify the unstated premise
  • Ask What must be assumed to make it either valid
    or strong?
  • Add a general claim that connects the premises
    and conclusion
  • Cheating example (12)
  • 1) This is the second time you caught her
    cheating.
  • 2) she shouldnt pass the class.
  • This argument becomes valid when we add this
    premise
  • 1.5)

18
Determining the Unstated premise
  • Now Ask Is the assumption reasonable?
  • Yes or No?
  • No, then determine what must be assumed to make
    the argument strong

19
Unstated premises Strong arguments
  • The bloodhound example (13)
  • 1) Moores dog is a bloodhound.
  • Thus, 2) Moores dog has a keen sense of smell.
  • What do we need to add to make this argument
    valid?
  • What do we need to add to make this argument
    strong?
About PowerShow.com