Susan Jacoby is the Author of The Age Of American Unreason, and she is really fascinating.  Her love of logic is reflected in all her work.  You could say she is an advocate for questioning the status quo and encouraging deep thinking.  Watch as she talks to Steven Colbert:

Her blog at the Washington Post: http://www.washingtonpost.com/blogs/spirited-atheist

Learn more about her and her work at:  http://www.susanjacoby.com/about.html

A spirited debater, she is, in my opinion, a welcome addition to any panel discussion.