1. Test the validity of the following arguments. Symbolize the propositions and use either a truth table or an informal proof.


1. If Manita loves cats, then Wipasiri loves dogs.
Wipasiri does not love dogs.
Therefore Manita does not love cats.

2. Either Manita loves cats, or Pattarika hates them.
But Pattarika does not hate cats.
So Manita loves cats.

3. Pailin has a pet lizard, and Pakorn has a sport car.
So either Pailian has a pet lizard, or Pakorn has a sport car.

4. Woravut loves doing math problems, or Athi loves playing soccer.
Therefore, Athai really loves playing soccer.

5. If Woravut loves doing math problems, then he is a good student.
Woravut is a good student.
Therefore, he loves doing math problems.

6. If Woravut loves doing math problems, then he is a good student.
Woravut does not love doing math problems.
So he is not a good student.

7. Pensuda is a BBA student, or Varidda is studying logic.
If Varidda is studying logic, then she loves the subject.
Therefore, Varidda loves logic.

8. Pensuda is a BBA student, and Varidda is studying logic.
It is not the case that, if Pensuda is a BBA student, then Varidda loves logic.
So either Varidda is studying logic, or she loves logic.

9. Phantira has a cat, if Neerada gives her one.
Neerada gives Phantira a cat, or she gives her a dog.
Therefore, Phantira actually has a cat.

10. Studying logic is a lot of fun, or else no one would bother studying it.
But a lot of people are studying it.
So it is a lot of fun!

2. Fill in the missing premise in the following enthymemes. Translate each sentence into categorical forms first.


Example: All who are Eric's friends love him, because he is generous.

Translation into categorical form:

Eric is a generous person
All generous people are those who are loved by their friends. THIS IS THE MISSING PREMISE.
So Eric is one who is loved by his friends (which means the same as "All who are Eric's friends love hiim.")


1. Everybody who is trying hard will succeed; therefore, Sakda will not succeed.

2. Since all countries who follow the IMF's program are pro-Western, Iraq is not pro-Western.

3. Thailand will be a darling of international investors again, because Thailand has assiduously follow the IMF's prescriptions.

4. Globalization will destroy the poor, because globalization only benefits the rich.

5. The demonstrators who gathered at the UNCTAD X all have legitimate agenda, because they are really concerned about the poor.

6. UNCTAD X is a marginalized meeting, because the US avoided it.

7. The man who threw a cake at Michel Camdessus is brave, because anyone who does this is liable for persecution.

8. Mike Moore is fat, therefore he is WTO president.

9. The IMF is the most hated organization in the world, because it is too powerful.

10. Since globalization will be a very powerful force, many people resent it.

These exercises are to be turned in on Tuesday, February 22, in class! Those who fail to turn them in will be deducted penalty points. HAVE FUN!

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