Homework #1: Deductive Arguments

Homework assignment #1 is due at the beginning of class on Monday, October 7th. It's worth 3% of your overall grade. The assignment is to complete the worksheet I hand out in class.

If you don'tt get it in class, you can download the worksheet here. Or, if you can't download it, here are the questions on the worksheet:

DIRECTIONS: Provide original examples of the following types of arguments (in premise/conclusion form), if possible. If it is not possible, explain why.

1. A valid deductive argument with one false premise.

2. An invalid deductive argument with all true premises.

3. An unsound deductive argument that is valid.

4. A sound deductive argument that is invalid.


MULTIPLE CHOICE: Circle the correct response. Only one answer choice is correct.

5. If a deductive argument is unsound, then:
a) it must be valid.
b) it must be invalid.
c) it could be valid or invalid.

6. If a deductive argument is unsound, then:
a) at least one premise must be false.
b) all the premises must be false.
c) all the premises must be true.
d) not enough info to determine.

7. If a deductive argument is unsound, then:
a) its conclusion must be false.
b) its conclusion must be true.
c) its conclusion could be true or false.

8. If a deductive argument’s conclusion is true:
a) then the argument must be valid.
b) then the argument must be invalid.
c) then the argument could be valid or invalid.

9. If a deductive argument is sound, then:
a) it must be valid.
b) it must be invalid.
c) it could be valid or invalid.

10. If a deductive argument is sound, then:
a) at least one premise must be false.
b) all the premises must be false.
c) all the premises must be true.
d) not enough info to determine.

11. If a deductive argument is sound, then:
a) its conclusion must be true.
b) its conclusion must be false.
c) its conclusion could be true or false.

12. If a deductive argument’s conclusion is false:
a) then the argument must be valid.
b) then the argument must be invalid.
c) then the argument could be valid or invalid.

Group Presentations

Here are the assigned groups for the group presentations on fallacies, along with your topics and the tentative date of each presentation (those dates may be pushed back):

1. Ad Hominem & Appeal to Force (October 28th): Dan M., Devon, Jesse, Marisa, Sonya
2. Appeal to Pity & Popular Appeal (October 28th): Claire, Dennis, Jabari, Lauren, Steve
3. Appeal to Ignorance & Begging the Question (October 28th): Dan T., Frank, Kathleen, Kimberly
4. Straw Man & Red Herring (October 28th): Chelsey, David, Jennifer, Matt L., Nestor
5. Appeal to Authority & False Dilemm2 (November 4th): Adam, Timothy, Travis, Udoka
6. Slippery Slope & The Naturalistic Fallacy (November 4th): Mike C., Michael M., Rebecca, Sean

If you haven't been assigned to a group yet, let me know as soon as possible. Below are more details about the presentation.

During our section on fallacies, groups of 4-5 students will present short lessons on two specific fallacies that their members have researched on their own.

Groups are free to choose how to present their topic to the rest of the class. Be creative! Think about puppets, posters, cartoons, songs, skits, handouts, whatever. Part of your grade will be based on how creative your presentation is. Remember, though, that you are expected to teach these fallacies to the rest of the class. Although they will have read about your fallacies in our textbook, the rest of class will probably not be as familiar with the material you are presenting as your group is. Here are some helpful suggestions of things to include in your presentation:

• DEFINITION: A formal definition of each fallacy
• A slow, clear explanation in plain English of what those definitions mean
• EXAMPLES: Lots of specific examples of arguments that commit each fallacy
• Explanations of how it is that these example arguments commit the fallacy
• WHY BAD?: An explanation of why each fallacy is a mistake in reasoning

I also recommend incorporating class participation of some form into your presentation. At the end of each presentation, the group will answer questions from the rest of the class.

The presentation is worth 150 points (15% of your overall grade). Except in unusual circumstances, each group member shall receive the same grade. There will not be any time set aside in class for groups to research and prepare for their presentation, so you should meet outside class to work on this presentation.

That Beyoncé Video WAS Great...

Why doesn't Kanye give a toast to the tools?

Maybe Kanye should just eat some cookies.

An Argument's Support

One of the trickier concepts to understand in this course is the structure (or support) of an argument. This is a more detailed explanation of the term (it's the same as the handout). If you've been struggling to understand this term, the following might help you.

An argument's structure is its underlying logic; the way the premises and conclusion logically relate to one another. The structure of an argument is entirely separate from the actual meaning of the premises. For instance, the following three arguments, even though they're talking about different things, have the exact same structure:

1) All tigers have stripes.
Tony is a tiger.
Tony has stripes.

2) All humans have wings.
Sean is a human.
Sean has wings.

3) All blurgles have glorps.
Xerxon is a blurgle.
Xerxon has glorps.

There are, of course, other, non-structural differences in these three arguments. For instance, the tiger argument is overall good, since it has a good structure AND true premises. The human/wings argument is overall bad, since it has a false premise. And the blurgles argument is just crazy, since it uses made up words. Still, all three arguments have the same underlying structure (a good structure):

All A's have B's.
x is an A.
x has B's.

Evaluating the structure of an argument is tricky. Here's the main idea regarding what counts as a good structure: the premises provide us with enough information for us to figure out the conclusion from them. In other words, the premises, if they were true, would logically show us that the conclusion is true. So, if you believed the premises, they would convince you that the conclusion is worth believing, too.

Note I did NOT say that the premises are actually true in a good-structured argument. Structure is only about truth-preservation, not about whether the premises are actually true or false. What's "truth preservation" mean? Well, truth-preserving arguments are those whose structures are such that if you stick in true premises, you get a true conclusion.

The premises you've actually stuck into this particular structure could be good (true) or bad (false). That's what makes evaluating an arg's structure so weird. To check the structure, you have to ignore what you actually know about the premises being true or false.

Good Structured Arguments
If we assume that all the premises are true, then the conclusion will also be true for an argument to have a good structure. Notice we are only assuming truth, not guaranteeing it. Again, this makes sense, because we’re truth-preservers: if the premises are true, the conclusion that follows will be true.

EXAMPLES:
1) All humans are mammals.
All mammals have hair.
All humans have hair.

2) If it snows, then it’s below 32 degrees.
It is snowing right now.
It’s below 32 degrees right now.

3) All humans are mammals.
All mammals have wings.
All humans have wings.

4) Either Yao is tall or Spud is tall.
Yao is not tall.
Therefore, Spud is tall.

Even though arguments 3 and 4 are ultimately bad, they still have good structure (their underlying form is good). The second premise of argument 3 is false—not all mammals have wings—but it has the same exact structure of argument 1—a good structure. Same with argument 4: the second premise is false (Yao Ming is about 7 feet tall), but the structure is good (it’s either this or that; it’s not this; therefore, it’s that).

To evaluate the structure, then, assume that all the premises are true. Imagine a world in which all the premises are true. In that world, are you able to figure out from the premises that the conclusion is also true? Or can you imagine a scenario in that world in which the premises are true, but the conclusion is still false? If you can imagine this situation, then the argument's structure is bad. If you cannot, then the argument is truth-preserving (inputting truths gives you a true output), and thus the structure is good.

Bad Structured Arguments
In an argument with a bad structure, you can’t draw the conclusion from the premises – the premises don’t give you enough information. Bad structured arguments do not preserve truth.

EXAMPLES:
1) All humans are mammals.
All whales are mammals.
All humans are whales.

2) If it snows, then it’s below 32 degrees.
It doesn’t snow.
It’s not below 32 degrees.

3) All humans are mammals.
All students in our class are mammals.
All students in our class are humans.

4) Either Yao is tall or Spud is short.
Yao is tall.
Spud is short.

Even though arguments 3 and 4 have all true premises and a true conclusion, they are still have a bad structure, because their form is bad. Argument 3 has the same exact structure as argument 1—a bad structure (it doesn’t preserve truth).

Even though in the real world the premises and conclusion of argument 3 are true, we can imagine a world in which all the premises of argument 3 are true, yet the conclusion is false. For instance, imagine that our school starts letting dogs take classes. The second premise would still be true, but the conclusion would then be false.

The same goes for argument 4: even though Spud is short (Spud Webb is around 5 feet tall), this argument doesn’t guarantee this. The structure is bad (it’s either this or that; it’s this; therefore, it’s that, too.). We can imagine a world in which Yao is tall, the first premise is true, and yet Spud is tall, too.

Extra Credit: Understanding a Long Argument

Reminder: No class tonight, September 23rd!

As mentioned in class last week, your next extra credit assignment is to read the following essay by Russian president Vladimir Putin in the New York Times:

• A Plea for Caution from Russia

Figure out Krugman's argument: what is his main point? What are his reasons supporting this main point? Paraphrase Krugman's argument in a clear premise/conclusion format and in your own words. Hand in your formal premise/conclusion version of Krugman's article at the beginning of class on Monday, September 30th.

Howard Sure Is a Duck

Howard the Duck is my favorite synecdoche for the 80's:

Homework: Email Subscription

So why does this course have a blog? Well, why is anything anything?

A blog is a website that works like a journal – users write posts that are sorted by date based on when they were written. You can find important course information (like assignments, due dates, reading schedules, etc.) on the blog. I’ll also be updating the blog throughout the semester, posting interesting items related to the stuff we’re currently discussing in class. You don't have to visit the blog if you don't want to. It's just a helpful resource. I've used a blog for this course a lot, and it's seemed helpful. Hopefully it can benefit our course, too.

Since I’ll be updating the blog a lot throughout the semester, you should check it frequently. There are, however, some convenient ways to do this without simply going to the blog each day. The best way to do this is by getting an email subscription, so any new blog post I write automatically gets emailed to you. (You can also subscribe to the rss feed, if you know what that means.) To get an email subscription:

1. Go to http://rowanlogic2013.blogspot.com.

2. At the main page, enter your email address at the top of the right column (under “EMAIL SUBSCRIPTION: Enter your Email”) and click the "Subscribe me!" button.

3. This will take you to a new page. Follow the directions under #2, where it says “To help stop spam, please type the text here that you see in the image below. Visually impaired or blind users should contact support by email.” Once you type the text, click the "Subscribe me!" button again.

4. You'll then get an email regarding the blog subscription. (Check your spam folder if you haven’t received an email after a day.) You have to confirm your registration. Do so by clicking on the "Click here to activate your account" link in the email you receive.

5. This will bring you to a page that says "Your subscription is confirmed!" Now you're subscribed.

If you are unsure whether you've subscribed, ask me (609-980-8367; landis@rowan.edu). I can check who's subscribed and who hasn't.