3.2a
Informal Argument Tree Diagrams

For this exercise, you are asked to do a little field work. As described in tutorial 3.2, we are looking to diagram and evaluate some real life informal (inductive and ampliative) reasoning.

One of the most common ways that the press presents reasoning is in the argument and rebuttal mode: "The Democrats say that we need to spend more money on health-care infrastructure but the Republicans contend that this is better accomplished by the private sector. Today in Congress..."...Well, you get the idea. And a quick survey of anything from Prime Time News Infotainment to the most stodgy foreign affairs journal will give you more of the same.

Field Work: Find an interesting argument of this type (as discussed in 3.2...maybe you'll find this argument on the Web), and think about it's argument types (a little causal argument here, a little argument from authority there), see how it's structured and how the rebuttal fits in.

Transfer the argument to Araucaria: Take this argument you've selected, perhaps simplify it a bit, save it as a .txt file, and open it in Araucaria. There are explicit directions for this: how to save a .txt file of your argument for Araucaria.

Add Scheme Files: You should already have 3_2.scm on your desktop. Open Araucaria, click Schemes, choose to Open Schemeset, and in the "Read Schemeset" box that pops up, find 3_2.scm by clicking this button: . (If you don't have this scheme file, it's best to unzip from this little program. Mac and other, download this file. The directions assume you've placed this on your desktop.)

Diagram your argument: Following the directions of 3.2, diagram your argument, identify the types of informal argument, identify the "owner", and try to evaluate cogency. Use the chocolate or global warming disputes as examples. (And there always is the Araucaria user's manual if you need help diagramming the rebuttal.)

• Often in reasoning, we leave out the obvious. I say "All men are mortal, so Jake is mortal". You know I've left out: "Jake is a man". No big deal. But sometimes a tacit premise is left out because addressing it squarely might be embarrasing to arguer! So it can be good to make our hidden assumptions explicit. Then we can examine them! To add a missing premise, just click .
• Real life disputation often involves an argument on one side with its point or conclusion and then a rebuttal argument with a counterpoint as conclusion. For marking a rebuttal explicit in Aracuaria: First, drag an arrow from your counterpoint to the orignal point; Second, click on your counterpoint and then on the rebuttal button: . (Careful! You need to follow these directions to make the thing work. You might want to practice with a simple argument.)

Hints: (1) I've found lots of nice sources for the point-counterpoint, argument-rebuttal form. There are some interesting ones about Al Gore's documentary on global warming. But it's just as easy to find them on home improvement strategies or the ethics of AIDS research on monkeys! See what you can find. (I'll paste some things at the end of this page too.)

(2) I've been sticking to fully inductive arguments. But many inductive arguments have deductive parts...we restate the evidence. About an investigation of some damaged vehicles:

All observed cases are immobile. So, no observed cases are mobile.

That's valid reasoning that could be a part of a statistical generalization argument. And you'll often see mathematical calculations or SL inferences. In fact, a standard scientific refutation of a hypothesis goes this way:

If my hypothesis H is true, the results R should be observed in the experiment.
But, to the contrary, ~R is true.
So, my hypothesis H is wrong.

Or:

H>R
~R
~H

Yes, this one is valid. And it has a familiar form! (What is it? One of those latin names...)

Source Ideas: You won't probably want to use any of these in particular, but it's the sort of thing you might find in your field work. So, here are a few that I just happened across.

Great stuff on pro-con arguments:

http://www.procon.org/

Endangered monkeys at heart of research fight

Scientists want to run AIDS experiments; animal rights activists horrified

http://www.msnbc.msn.com/id/12212797/?GT1=7938

# Exx-Cons

Post date 05.25.06 | Issue date 06.12.06

Al Gore seems to have touched a nerve. An Inconvenient Truth, his new documentary about global warming--a simultaneously frightening and inspiring film--hadn't yet arrived in theaters last week when a guerrilla movement to discredit the movie had already begun. A network of oil-funded think tankers and conservative media outlets have joined arms to launch the most massive offensive against a PowerPoint presentation ever recorded by man. But there is one salutary effect of this new campaign. The Swift-Boating of An Inconvenient Truth has brought into public view yet another shining star in the right's anti-science constellation. While the fundamentalist theo-conservatives sowed doubts about evolution during the debate over "intelligent design," the Exxon conservatives are storming into battle against global warming.

http://3quarksdaily.blogs.com/3quarksdaily/2006/06/another_shining.html

Hmm...that link seems to be bad. But up pop's a McCain-Obama dispute about who's the phony: Worth working on: http://www.tnr.com/politics/story.html?id=9f9b36f8-f297-4a48-9574-f231803be083