1. Invitation to Critical Thinking Chapter 10
Lecture Notes
Chapter 10
Invitation to Critical Thinking Chapter 10

2. Invitation to Critical Thinking Chapter 10
Overview
Evaluating Premises: Self-evidence, Consistency, and Indirect Proof
Tautologies
Truisms by Definition
Contingent Claims
Values Relativism
Self-evident Claims
Beyond Self-evident Claims
Consistency
Implications
Invitation to Critical Thinking Chapter 10

3. Invitation to Critical Thinking Chapter 10
Evaluating Premises
All arguments have to start somewhere
Every argument will have unsupported premises
When designing and constructing an argument, establish as firm a foundation as possible
Experienced arguers use the most “basic” premises as claims
uncontroversial
as easy to accept
as hard to challenge or refute
Two “basic” premises or claims are tautologies and truisms by definition
Invitation to Critical Thinking Chapter 10

4. Invitation to Critical Thinking Chapter 10
Tautologies
A claim that you can't deny without formally contradicting yourself
considered to be necessarily true
though tautologies always carry the value “true,” they don't convey much information
Invitation to Critical Thinking Chapter 10

5. Invitation to Critical Thinking Chapter 10
Example of Tautology
Either the President knew in advance of the arms-for-hostages deal or he didn't.
If he did know of the arms-for-hostages deal in advance, then he's involved in the cover-up and therefore unworthy of his office.
If he didn't know of the arms-for-hostages deal in advance, then he's not in control of his own administration, and is therefore unworthy of his office.
Therefore, either way, he’s definitely unworthy of his office.
Invitation to Critical Thinking Chapter 10

6. Invitation to Critical Thinking Chapter 10
Truisms by Definition
The terms of the claim reveal the truth of the statement
Anyone who understands the meanings of the terms in the claim will immediately recognize any such statement as true
Invitation to Critical Thinking Chapter 10

7. Examples of Truism by Definition
Murder is a form of homicide
All bachelors are unmarried
Invitation to Critical Thinking Chapter 10

8. Invitation to Critical Thinking Chapter 10
Contingent Claims
Claims that are neither self-contradictory nor necessarily true are called contingent
Contingent claims’ truth or falsity depends on something outside of themselves
Something beyond their formal structures
Something beyond the meanings of their terms
Invitation to Critical Thinking Chapter 10

9. When Evaluating Contingent Claims, ask
What kind of claim is being made here?
Does the premise make a factual claim or an evaluative claim?
Does it offer an interpretation?
What sort of issue does it raise?
What sorts of additional support might this claim need?
Invitation to Critical Thinking Chapter 10

10. Examples of Contingent Claims
All men are created equal
Not all men are created equal
Some men are created unequal
Invitation to Critical Thinking Chapter 10

11. Invitation to Critical Thinking Chapter 10
Values Relativism
More reasonable and understandable than Relativism in general
because evaluative issues (which cannot be resolved by doing science or looking things up generally) are harder to resolve than factual issues
Some hold that values relativism can't be done due to the essential difference and an unbridgeable gap between facts and values
It doesn't follow from the fact that evaluative claims can't be established empirically that they can't be established at all
To resolve evaluative claims, consider and evaluate the best available arguments on all sides of the issue
Invitation to Critical Thinking Chapter 10

12. Invitation to Critical Thinking Chapter 10
Self-evident Claims
Self-evident claims: the supporting claims are no more basic or evident than what they support
To support them by appeal to further observations would be no more basic or evident than what they support
Unless there is good reason for doubting them, such claims may be taken as self-evident
Invitation to Critical Thinking Chapter 10

13. Examples of Self-evident Claims
Human life is precious
Peace is precious
Freedom is better than colonial bondage as a way of life
Basic human rights belong equally to each and every human being
Invitation to Critical Thinking Chapter 10

14. Beyond Self-evident Claims
To determine if a claim is beyond a self-evident claim, ask
Is it an interpretation?
This means other interpretations are possible
This means this is an interpretive issue
An interpretation is the kind of claim one can always legitimately be challenged to argue for
No single simple procedure for resolving interpretive issues exists
No single simple procedure for establishing interpretive claims as premises in an argument exists
To evaluate it
Consider the best arguments that can be made for and against the claim
Weigh up the arguments and the evidence on all sides
Invitation to Critical Thinking Chapter 10

15. Invitation to Critical Thinking Chapter 10
Consistency of Claims
Consistency is crucial to our understanding of deductive validity, but because inconsistency is always a sign that something is wrong somewhere.
If a given set of claims as a group is internally inconsistent, then although you may not know which of the premises is false, you know they can't all be true.
Invitation to Critical Thinking Chapter 10

16. Implications of Claims
If a claim leads by implication to any further claim that is self-contradictory, or otherwise absurd or known to be false, then there is good reason to doubt the claim.
This strategy has traditionally been known by its Latin name Reductio ad Absurdum (which means to reduce to absurdity).
The strategy can also be inverted to use in defense of a position.
Invitation to Critical Thinking Chapter 10