Our third and final class on the traditional Aristotelian Logic, taught by Fr Steven Ledinich LPh, Phd. In this class we continue our study of the third act of the intellect, Reasoning with more work on the Syllogism practice exercises starting from question 3 - please see below. We then move on to learn about the Fallacy - the invalid argument. All exercises referred to in the class are included below.

Logic Questions - continued from the second class

3. No one complains about a generous person. No one complains about John, so John is a generous person.

4. Some violent people have a criminal record. We know this because no policemen have a criminal record yet some policemen are violent people.

5. We know that chalk becomes marble when crystallized by heat and pressure. This is because all chalk is limestone, and some limestone becomes marble when crystallized in such a fashion.

9. Write the conclusion to these syllogisms: (8)
1. Every professor has a university degree.
Not all intelligent people have university degrees.

2. Every possum is a tree-dwelling mammal.
Every possum has a long tail.

3. Not every rose bush is disease resistant.
Every rose bush is a plant.

4. No rose is in bloom.
Every plant in my garden is in bloom.

10. State if the following hypothetical syllogisms are valid or invalid. If invalid, state the rule which is violated: (6)
1. If the oxygen supply in the lake is low, the fish will die. But we know that the fish did die. Therefore, the oxygen supply must be low.

2. If the Australian soccer team trains hard, it will qualify for the final. But what happened is that it failed to qualify for the final. Therefore, the Australian soccer team failed to train hard.

3. I think that everyone would agree that if the students studied for their exams, they would pass them. But we know that the students didn’t study and therefore they won’t pass their exams.
11. Expand the following enthymenes: (12)

1. It is clear that all fossil fuel pollution causes climate change. The scientific community knows this because all such pollution causes an increase in CO2 levels.

2. No Labor candidate should be voted in because every one of them is controlled by the unions.

3. It is clear that water is not a fuel because it is not combustible.

4. Some dangerous things are combustible because all fuel is dangerous.

12. 1. What is a fallacy? (2)

2. Give the primary fallacy for each of the following: (10)

a) Use Gillette razors. Roger Federer does.

b) To allow every person unbounded freedom of speech must always be, on the whole, advantageous to the state; for it is highly favourable to the interests of the community that each individual should enjoy a liberty, perfectly unlimited, of expressing his sentiments.

c) Analysts are convinced that the stock market will remain strong next year because it was strong over the last three years.

d) All Catholics must be holy. Look how holy John is, and he’s a Catholic.

e) That man must be a lawyer because he is good at arguing.

f) Those prisoners learnt some important lessons while in prison. Therefore, spending time in prison is always a good thing.

g) When are you going to stop being rude to me?

h) A person is happy because he has a lot of money.

i) Senator Green stood up and said: “You should not believe Senator Pius’s lengthy arguments for why marriage has to be between a man and a woman because the real reason he opposes this same-sex marriage bill is because he is homophobic.”

j) Man is only material because he is only made up of bone, muscle and other tissue.

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