What's the difference between a business case and a rationalization?
Winning business depends entirely on the ability to constitute credibility in a given situation. If those you're pitching accept your argument, you win. If they don't, you have to go back to the drawing board.
Rhetorical fluency is one of the best examples of a direct application of a liberal arts education to successful business practice.
I particularly like Stanford's website for a variety of definitions as well as blogs on the topic.