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Lecture 4

# PHI 1101 Lecture Notes - Lecture 4: Deductive Reasoning, Statistical Syllogism, Pre-Medical

Department
Philosophy
Course Code
PHI 1101
Professor
Sardar Hosseini
Lecture
4

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Monday, September 28, 2015
Class 4
Chapter 3: Evaluating Arguments
The Three Steps
1. Recognizing Arguments (chapter 1)
2. Analyzing Arguments (chapter 2)
3. Evaluating Arguments (chapter 3,4,5,6,7)
-The purpose of analyzing arguments (presenting arguments in standard form
+diagrams) is to aid their evaluation
-The purpose of evaluating an argument is to know whether or not a given argument is
a good one
-We discuss different ways of ding this, some will come in greater details in chapters
4,5,6 and 7
Examples
-What is the difference between arguments 1 and 2?
1. John is armed.
So, John is dangerous.
2. All men are mortals.
Socrates is a man.
Therefore, Socrates is mortal.
3. John is armed.
John is a police ofﬁcer.
So, John is dangerous.
^ doesn’t make sense
Two Types of Arguments
1

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Monday, September 28, 2015
1. Deductive Arguments (Deduction or Syllogism):
-In deductive arguments, the premises are meant to guarantee the conclusion 100%
-it is an argument intended to provide logically conclusive support for it’s conclusion.
-Final, deﬁnitive, undeniable support.
-Deductive arguments are characterized as valid or invalid.
2. Non-deductive Arguments (Induction):
-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
Deductive Arguments
-Let’s look at these examples:
1. If: A=B"
B=C"
Therefore, A=C
2. All men are mortals."
Socrates is a man."
Therefore, Socrates is mortal.
3. If whales are mammals, they have lungs."
Whales are mammals."
Therefore, whales have lungs.
More Examples:
-Everyone in the year yesterday was exposed to the virus, and you were there then.
That means that you were exposed to the virus.
-James I was monarch before Charles I. And Charles was monarch before Charles II.
Thus, James I was monarch before Charles II.
-Harold is Matilda’s son. So, Matilda is Harold’s mother.
Non-deductive Arguments
2