This isn't just a rhetorical question. It isn't usually philosophers like Habermas who set the tone in popular discussions of what "reason" is or what is "reasonable."
I saw Ringer's top-listed book in the office tower lobby the building over from where I work. The lobby used as a little marketplace for vendors. I promise you you won't find a copy of Capital there.
Also relates to the discussion about habermas and "reason":
http://www.amazon.com/exec/obidos/ASIN/0399146865/qid=997989281/sr=2-1/104-5411466-7333565
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Peter Kosenko