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© 2014 Pacific Crest
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If A, then B; not A, therefore not B
Example
: If the woman is smiling then she is happy. Just because the woman is not smiling does
not mean that she is not happy.
Why?
If A implies B and you do not have A, it doesn’t mean
that you cannot have B.
The general truth table for the
proposition it at right; an expanded and specific truth
table is shown below.
(IF) A
(THEN) B A
→
B
the woman is smiling
she is happy
True
the woman is smiling she is NOT happy False
the woman is NOT smiling she is happy
True
the woman is NOT smiling she is NOT happy True
A
B A
→
B
True True True
True False False
False True True
False False True
A
re You Ready?
Before continuing, you should be able to ...
I can...
OR
Here’s my question...
interpret a truth table result
determine if an argument is true
identify a typical type of fallacy
explain why each step in a proof works
P
lan
How to complete the activity
1. Share two discoveries from the preparation exercise with your team members.
2. Review the Critical Thinking Questions before analyzing the models
3. Analyze each model using the Critical Thinking Questions to help you explore the models.
4. Answer the Critical Thinking Questions.
5. Browse through the Oops sections of each activity to this point and see how the examples shown
there relate to this experience.
6. Complete the remainder of this activity (from Demonstrate Your Understanding through Assessing
Your Performance) on your own, or as directed by your instructor.
2.2 Logical Reasoning