Friday, April 17, 2026

Practice Quiz #3

Identify the most obvious fallacy committed by each of the following arguments.  You may give a brief explanation for your answer (on the back if necessary).

1. Every member of Congress is under 100 years old.  Therefore, Congress must be under 100 years old.

 

2. You can’t tell me to stop eating cows, you’re wearing leather shoes!

 

3. Last time I ordered a veggie burger, I lost my car keys.  I’m staying away from vegan food from now on!

 

4. We can’t know whether lobsters can suffer; therefore, eating them is perfectly morally permissible.

 

5. I’m sticking to a meat-based diet.  My piano teacher told me that vegans are protein deficient.

 

6. As the saying goes, “beauty is beneath the skin.”  Therefore, the true beauty of an apple is to be found in its core.

 

7. Any vote for Bernie Sanders was sexist, since either you supported Hilary Clinton, or you were opposed to having a woman in the oval office.

 

8. You should vote for Trump unless you want MAGA protesters to burn down your house.

 

9. Vegans are unhealthy because they chose an unhealthy diet.

 

10. My sister thinks we should stop sending money and bombs to Ukraine.  Well, isn’t that just what Putin wants us to do?  I don’t listen to Putin-puppets and lovers of all-things-Russian.

 

 

Monday, April 13, 2026

Wednesday, April 1, 2026

Assignment #7: Informal Fallacies; Quiz #3

1. Begin reading: Hurley, "Informal Fallacies":

Informal fallacies

Reminder: quiz #3, this coming Wednesday, 5 Venn diagram proofs lifted directly from exercise 21.


Wednesday, March 25, 2026

extra credit, quiz #2

 Translate into formal language and show validity:

If you want to avoid silly errors in life or maximize your intellectual potential, then you should choose to study logic. No doubt you do want to maximize your intellectual potential and be the best student you can be. If you do choose to study logic, then you will be in charge of your life.  Therefore, you will indeed be in charge of your life.  (Use A, M, L, B and C)

Friday, March 13, 2026

Assignment #6: Formal Methods II: Categorical Logic

1. Read Van Cleave, section 2.14; do exercise set 18.

2. Read 2.17; do exercise set 21.





















Practice Quiz #2

 We will review this practice quiz on Monday, March 23; we will have quiz #2 on Wednesday, March 25

1. Reproduce the chart for induction and deduction.

2. Write a sound deductive inference.

3. Write a strong inductive inference.

4. Translate into formal symbolic language:

a. I will go to the party only if you will go (use I and Y).

b. It is not both sunny and warm today (use S and W).

c. It is neither sunny nor warm today (use S and W)

5. Is the following inference valid or invalid:

If A then B; not A, therefore, not B.

Show validity using the 8 rules of deduction:

1. Q

2. P   /therefore, (Q or R) and P



1. If A then B

2. not B and not C  /therefore, not A and not C



1. If D or E, then A and B

2. D   /therefore, B



1. If P then Q

2. P or (R and S)  

3. not Q and not T   /therefore, R


Translate and show validity using the 8 rules of deductive reasoning:

If you care about your education, you will succeed; and if you succeed, your years at MCLA will be spent wisely. You do care about your education, and you will either fail to spend your years at MCLA wisely or you will reap one of life's greatest rewards. It follows that you will reap that reward. (use C, S, Y, R)

Monday, March 2, 2026

Assignment #5: Formal Proofs

Read: Van Cleave, section 2.11. Do exercise sets 16 & 17.

8 Rules of valid inference:

Modus Ponens (MP)

pq,
p

q

 Modus Tollens (MT)

 pq,
~q

~p

 Disjunctive Syllogism (DS)

pq,
~p

q

 or, if desired,

pq,
~q

p

Simplication (Simp)

p.q

p

 or, if desired,

p.q

q

Conjunction (Conj)

p,
q

p.q

Hypothetical Syllogism (HS)

pq,
q
r

p
r

Addition(Add)

 p


p
q

 Constructive Dilemma (CD)

(pq),
(r
s),
p
r

q
s