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Lecture 6

This

**preview**shows half of the first page. to view the full**2 pages of the document.**Analyzing and Evaluating Arguments

Lecture 6-PHI1101

Analyzing: Presenting argument sin standard form with diagrams, aid in the evaluation

Evaluating: Know whether or not a given argument is a good one

Two Types of Arguments

Deductive (Syllogism): In deductive arguments, the premises are meant to guarantee the

conclusion (100%)

- It is an argument intended to provide logically conclusive support for its conclusion. Not

a matter of degree.

- Final, deﬁnitive, undeniable support.

- Deductive arguments are characterized as valid or invalid.

Non-Deductive: In non-deductive arguments, the premises are meant to confer some high

degree of probability on the conclusion (99% or less)

- When we evaluate deductive arguments we describe them as either successful or

unsuccessful.

Evaluating Deductive Arguments

Truth: Truth or falsity only applies to single statements or claims (premises and conclusion)

Validity: Validity is a matter of the support that a set of premises lends to a conclusion. It is a

relationship (Structure) hold between premises and conclusion

- Validity does not require the premises of an arguments to be true

Soundness: A valid argument with all true premises and a true conclusion is called a sound

argument

- But, what exactly are the valid/invalid and sound.unsound arguments?

AN INVALID ARGUMENT MAY NEVER BE A SOUND ARGUMENT

More…

When evaluating any arguments, we ask two independent questions:

1. Are the premises true? Or false?

2. How much support its premises provide for the conclusion?

- These two questions are independent

Four possibilities

1. False premises and a false conclusion (Valid)

2. False premises and a true conclusion (Valid)

3. True premises and a true conclusion (Valid and Sound)

4. True premises and a false conclusion (Invalid)

PULL EXAMPLES OFF POWERPOINT FROM BLACKBOARD

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