I like the diagrams. I found the inclusion and exclusion circles Epstein's Critical Thinking particularly helpful. The concept: Everyone included in the circle has the quality the circle is talking about.
The little cartoon of Lee and Maria on p. 167 is a good example. The argument presented is
- Every philosophy professor reasons well (Large Circle)
- No philosophy professor is a politician. (Smaller Circle inside the Large Circle)
Therefore - No politician reasons well. (Small Circle outside the Large Circle)
But if you use that for an argument, you are saying that everyone who is not a philosophy professor does not reason well. Although it may be true of politician, we know it's not true of EVERYONE. No, that's not true. For that be be true, the Circle for everyone who is a philosophy professor and everyone who reasons well would be the same! So, instead you MIGHT be indicating that everyone who is not a politician. including philosophy professors, reasons well. HA!
Maria then amends the drawing to indicate that some politicians reason well by making the politician circle overlap the Large 'Reasons Well' circle. So, some do. I suppose, the smaller the overlap, the smaller the percentage included.
I think you did a good job of explaining how to test for validity for general claims. I liked the way you broke it down into diagrams. I similarly did the same subject on one of my posts, but didn't explain it as well, so it was a good read for me. I actually did on cell phones and electronics, but it was really hard for my to categorized the areas in which each sentence belonged. I liked the example you chose because it is so on the money also, especially what these crooks are doing in Washington! So I really liked your post.
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