Monday's discussion:

These concepts were introduced:

• Sufficient Condition
• Necessary Condition
• Necessary & Sufficient Condition(s)

We talked about arguments:

• x is an argument if and only if:
• x is a valid argument if and only if:
• x is an sound argument if and only if:

We practiced identifying arguments, i.e., identifying conclusions and premises, figuring out if the argument is valid or invalid (and added missing premises to make them valid, if needed), and whether the argument is sound or not. Here were the examples:

Consider the arguments given below. Identify the conclusions of each passage. Identify the premises.

If the argument is valid, state the logical form of the argument (e.g., modus ponens). If the argument is invalid, explain state the name of the fallacy (e.g., affirming the consequent).

If the argument is valid, state whether it is sound or not (i.e., whether the premises are true).

1. “George Bush is the president now. If he’s the president, he works for the government. So, Bush works for the government.” Valid? Sound?

2. “John Kerry is the president now. If he’s the president, he works for the government. So, Kerry works for the government.” Valid? Sound?

3. “Abortion is not wrong. If it’s wrong, then it’s illegal. But, it’s not illegal. So, it’s not wrong.” Valid? Sound?

4. “If Bob plays professional basketball, then he’s over 4 feet tall. Bob is over 4 feet tall, so he’s a professional basketball player.” Valid? Sound?

5. “If having the death penalty prevents future crime, then it’s right to have it. However, the death penalty does not prevent future crime (at least, that’s what most of the studies show). So it’s wrong for us to have the death penalty.”

Valid? Sound?

6. “Either a fetus is a ‘person’ or the fetus is not a ‘person.’ It’s not true that the fetus is not a ‘person.’ So, the fetus is a ‘person.’ It’s wrong to kill ‘persons.’ Since the fetus is a person, abortion is wrong.” Valid? Sound?

7. “If everything has a cause, then all our behavior is caused. If all our behavior is caused, then we are like robots. If we are like robots, then we aren’t free. But we are free, so it’s not true that everything has a cause.” Valid? Sound?

8. “Either the world had a beginning or it did not have a beginning. Obviously the world did not NOT have a beginning, since if there were no beginning there would be no world. But there is a world, so the world had a beginning. Therefore God exists.”

Valid? Sound?

9. “Some say that ‘Might makes right.’ But if that view were true, then it’d be OK for strong people to beat-up weaker people whenever they wanted. But that’s not OK, so it’s not true that ‘Might makes right.’ Whatever makes ‘right’ isn’t ‘might’!” Valid? Sound?

10. “Some say that a woman has a right to do whatever she wants with her body. But if this were true, then a woman would have a right to sell her body as a prostitute, and she would have the right to use her body to kill other people. But women don’t have these rights, so women don’t have rights to do whatever they want with their bodies.” Valid? Sound?