Tony,

RE:  red herring of “the correct definition of ‘argument’”

I agree with the main point of your post, viz., what function of arguments should be emphasized in a CT course. 

That said, I don’t see the red herring part.  The discussion about definition reminds me of Locke’s famous treatment in the Essay, retweeted by Voltaire as “Define your terms.”  Isn’t that where critical thinking begins?  In the case of “argument,” the task may be mundane, even trivial, but not a distraction.

Best regards,

Daryl

N. B.  There are likely core disagreements about arguments being essentially persuasive rather than justificatory because we are each operating with possibly different theories of meaning (deliberately or not).  Some of us may think that meaning emerges from Gricean intentions, especially the speaker’s desire to cause a belief in the listener.  Others of us may take a non-mentalistic view in which meaning is based on use that is characterized independently of speaker intentions or beliefs (Davidson?, Kripke?).  The latter take is relevant to CT because the principle of charity instructs us to understand another person’s speech in a way that best accords with the facts or what is true; Davidson’s “rational accommodation.”  There are other versions of the principle of charity, of course.  Just some thoughts.