Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 1 3 Logic The Study of...
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Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 1 3 Logic The Study of What’s True or False or Somewhere in Between 3
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Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 3 Verifying Arguments3.4 Recognize some common valid argument forms Recognize some common fallacies
Transcript of Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 1 3 Logic The Study of...
Copyright © 2014, 2010, 2007 Pearson Education, Inc.Section 3.4, Slide 1
3 Logic
The Study of What’s True or False or Somewhere in Between
3
Copyright © 2014, 2010, 2007 Pearson Education, Inc.Section 3.4, Slide 2
Verifying Arguments3.4
• Use truth tables to show an argument to be valid
• Understand how a truth table can show an argument to be invalid
(continued on next slide)
Copyright © 2014, 2010, 2007 Pearson Education, Inc.Section 3.4, Slide 3
Verifying Arguments3.4
• Recognize some common valid argument forms
• Recognize some common fallacies
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 4
Verifying Arguments
Representations of arguments:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 5
Verifying Arguments
• Truth table for :p q p q
Because this statement is a tautology, the argument is valid.
The form is called the law of detachment. p q p q
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 6
Verifying Arguments
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 7
Verifying Arguments
• Example:
(solution on next slide)
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 8
Verifying Arguments
• Example:
(solution on next slide)
p u
Symbolically:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 9
Verifying Arguments
• Solution:
is called the law of contraposition.
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 10
Invalid Arguments
• Example:
(solution on next slide)
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 11
Invalid Arguments
• Example:
(solution on next slide)
c ffc
c f f c
Symbolically:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 12
Verifying Arguments
• Solution:
One or more F’s in the truth table means the argument is invalid.
c f f c
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 13
Verifying Arguments
• is called the fallacy of the converse. c f f c
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 14
Valid Argument Forms and Fallacies
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 15
Verifying Arguments
• Example: Identify the form of the argument and state whether it is valid.
• Solution:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 16
Verifying Arguments
• Example: Identify the form of the argument and state whether it is valid.
• Solution:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 17
Verifying Arguments
• Example: Identify the form of the argument and state whether it is valid.
• Solution:
Copyright © 2014, 2010, 2007 Pearson Education, Inc. Section 3.4, Slide 18
Verifying Arguments
• Example: Identify the form of the argument and state whether it is valid.
• Solution:
