1. Evaluating Arguments
Jason M. Chang
Critical Thinking

2. Lecture Outline Background A condition R condition G condition
Using the ARG conditions

3. Background Evaluating arguments
Evaluating arguments involves determining whether the argument is “good” (i.e., “sound” or “cogent”)

4. Background How to evaluate
Use criteria to determine whether the thing being evaluated is “good” or “bad”
Examples?
Examples of evaluating something
Evaluating a restaurant
Good food
Good service
Clean and sanitary
Reasonable pricing

5. Three criteria for evaluating arguments
Background
A – Acceptable premises
R – Relevant premises
G – Good grounds
Three criteria for evaluating arguments

6. (A) Acceptability of Premises
A good argument must have acceptable premises
(P1) All women are rich.
(P2) Socrates is a woman.
Therefore,
(C) Socrates is rich.
(P1) If we allow same-sex marriage (SSM), society will collapse.
(P2) We’ve allowed SSM.
Therefore,
(C) Society will collapse.
Does not matter how impeccable the logic is
(P1) Either you attend church or you are an evil person.
(P2) You don’t attend church.
Therefore,
(C) You are an evil person.

7. (A) Acceptability of Premises
Acceptability VS. Truth
Why does the book use acceptability instead of truth?
Does not matter how impeccable the logic is

8. (A) Acceptability of Premises
Acceptability VS. Truth
Reason #1: A premise can be acceptable without knowing it is true
(P1) It will rain tomorrow. Therefore,
(C) You should set out your jacket
Does not matter how impeccable the logic is

9. (A) Acceptability of Premises
Acceptability VS. Truth
Reason #2: A premise can be acceptable without it being true for everybody
(P1) We should choose a destination that has _______. (P2) Hawaii has _______.
Therefore,
(C) We should go to Hawaii.
Example – convincing the family that annual vacation should be in Hawaii this year
(P1) We should choose a destination that has _________.
(P2) Hawaii has ____________.
Therefore,
(C) We should choose Hawaii
Wife – good shopping
Brother – good food
Teenage son – good surfing
Teenage daughter – hot guys
Ethical question
Is it ethical to use knowingly false premises to argue for something?

10. (A) Acceptability of Premises
Acceptability VS. Truth
Reason #3: Charity
(P1) The archaeopteryx’s main feathers show the asymmetric, aerodynamic form typical of modern birds.
(P2) The asymmetric, aerodynamic form of feathers is evolved to aid in flying.
Therefore,
(C) The feathers of the Archaeopteryx must have been used for flying.

11. (R) Relevance of Premises
A good argument must have relevant premises
A premise is relevant to the conclusion if it provides some evidence or reason for the conclusion

12. (R) Relevance of Premises
Relevant premises?
(P1) Smith has an appendicitis, gout, and bladder cancer.
Therefore,
(C) Smith is not healthy enough to run a marathon.
(P1) Basketball is a game in which height contributes toward one’s success.
Therefore
(C) Basketball is a game for which physical characteristics make a difference

13. (R) Relevance of Premises
Same subject does not necessarily suggest relevance
(P1) I went to the party. Therefore,
(C) The party was fun
(P1) Philosophy is fun.
Therefore,
(C) Philosophy is difficult.

14. (R) Relevance of Premises
Relevance does not necessarily suggest enough support
(P1) Guns are the cause of tens of thousands of deaths each year. Therefore,
(C) We should ban guns.
(P1) I attended and participated in every class. Therefore,
(C) I should pass the class.
30,000-35,000 gun deaths in the U.S.

15. (G) Good Grounds
(P1) Guns are the cause of tens of thousands of deaths each year. Therefore,
(C) We should ban guns.
(P1) I attended and participated in every class. Therefore,
(C) I should pass the class.
It is possible have relevant premises that fail to give enough support for the conclusion

16. (G) Good Grounds
A good argument must have premises that give good grounds for the conclusion
Premises give good grounds for the conclusion if they provide enough support for the conclusion
NOTE: If the premises give good grounds, they must be relevant (but not vice versa).

17. (G) Good Grounds Form of argument
Arguments that use information (e.g., numbers, statistics)
How it can fail G
Fails to account for all relevant information
(P1) Cars are the cause of over 35,000 deaths each year in the U.S.
Therefore,
(C) We should ban cars.

18. (G) Good Grounds Form of argument
Arguments that make a generalization from a sample
How it can fail G
Inadequate sample (e.g., small sample size)
(P1) I met 3 Parisians in my life.
(P2) All 3 smoked.
Therefore,
(C) All Parisians smoke.

19. (G) Good Grounds Form of argument
Arguments that derive cause from effect
How it can fail G
Fails to account for all possible causal factors
(P1) The two boys behind the Columbine school shooting were fans of The Matrix.
Therefore,
(C) To protect our children, The Matrix should removed from video store shelves.

20. Using the ARG conditions

21. Using the ARG Conditions
Evaluating arguments
Check the premises for their acceptability
Check the premises for their relevance to the conclusion
Check the premises to ensure they give goods grounds for the conclusion
If all three, the argument is cogent

22. Using the ARG Conditions
(P1)
(P2)
So,
(P3)
(P4)
Therefore,
(C)
Arguments with subarguments
The subargument must also meet ARG
Subarguments must be evaluated independently from the main argument
Must meet ARG
Must meet ARG

23. Using the ARG Conditions
If the argument meets all ARG, you are rationally committed to accepting the conclusion
An argument can fail the ARG even if you the conclusion is true