Laura Redeihs sent me this link to an interesting tool for critical thinking. Basically it is a discussion board which requires the users to state their claims in terms of numbered premises and conclusions. People who reply have to post a criticism of either a premise the conclusion, and all posts are rated by the whole community on an agreement scale.
This has a fuck of a lot of promise, and is free to boot. The main problem is that there aren't many arguments up yet, and the ones that have been posted are of mixed quality. I imagine that this will change as the site gains popularity.
The only other problem I have so far is that there is no formal mechanism for distinguishing criticisms of the truth of a premise from criticisms of the validity of an inference. Consider this argument. The move from premise 1 to premise 2 is clearly invalid: he is concluding actuality from possibility. However premise 2 is clearly true. He really could have just started the argument there. It would be nice if the structure of the discussion board allowed me to post a criticism of the inference that is marked as such.
I'm going to send my reasoning students to this site during the upcoming semester. I have a week devoted to computer assisted analysis of argument structure, and this would fit in there.
In the mean time, I'm going to post a few classic arguments and wander around for a while.