Read: Van Cleave, section 2.11. Do exercise sets 16 & 17.
8 Rules of valid inference:
Modus
Ponens (MP)
p⊃q,
p
∴
q
Modus Tollens (MT)
p⊃q,
~q
∴
~p
Disjunctive Syllogism (DS)
p∨q,
~p
∴
q
p∨q,
~q
∴
p
Simplication (Simp)
p.q
∴
p
p.q
∴
q
Conjunction (Conj)
p,
q
∴
p.q
Hypothetical Syllogism (HS)
p⊃q,
q⊃r
∴
p⊃r
Addition(Add)
∴
p∨q
Constructive Dilemma (CD)
(p⊃q),
(r⊃s),
p∨r
∴
q∨s
Sample Quiz #1
1. What is a logical argument?
2. List 2 premise indicator words and 2 conclusion indicator
words.
3. Distinguish arguments from explanations among the following:
a. “All dogs are reptiles; Fido is a dog; therefore, Fido is
a reptile.” B. “Go to your room, because you have been bad, and all bad persons
must go to their rooms.” C. “Water
freezes at 32 degrees because the
molecules get so cold that they slow down enough to hook onto each other,
forming a solid crystal.”
4. What are the possible ways an argument can be unsound?
5. True or
false? “A sound deduction may have one
false premise.”
6. Reproduce the chart for induction and deduction.
7. Compose an enthymeme, then supply the missing premise.
8. Translate into
formal symbolic language:
a. It is Friday and it is not raining. (use F and R)
b. My name is not Bob or Sally. (use B and S)
c. Next week, we will meet on Monday or Wednesday, but not Tuesday or Thursday. (use M, W, T, R)
d. I'll have some cake or ice cream, but not both. (use C and I)
9. Write an argument
that attempts to leap over the “is-ought gap.”
What missing premise would make it valid?
10. Reproduce the
truth table for "and".
Reminder; Quiz #1, Monday, 10/6
Begin reading and working through the exercises in Van Cleave, 1.3; and 1.6-1.9
Supplemental (on the is-ought gap):
Things to do:
1. We will continue discussing the nature of philosophy/critical thinking in our next session.
2. Begin reading Van Cleave, 1.1-1.2. In your notebook dedicated to this class, do all of the exercises. Bring questions/comments to class.
Things to do:
