PHI 1101 Lecture Notes - Lecture 6: Deductive Reasoning, Soundness, Convulsion
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Analyzing and Evaluating Arguments
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
- 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
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
- But, what exactly are the valid/invalid and sound.unsound arguments?
AN INVALID ARGUMENT MAY NEVER BE A SOUND ARGUMENT
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
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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