Rhetoric?

I have heard the word rhetoric only once, and that was when my Communications major roommate was trying to decipher the meaning for a class. What I got out of that conversation was that rhetoric is speech (both formal speeches and everyday communicating) and the kind of language and means used to deliver and receive that speech. After reading James A. Herrick’s "An Overview of Rhetoric" I think my definition was pretty much on the money with a few exceptions. I need to include the aspect of persuasion from my definition. Mainly though, he mentions many times the two categories of: 1) what was said and 2) how it was said, or the content and form respectively, which is a much more clear way to phrase what I tried to articulate. It’s not surprising though that “rhetoric” is a commonly used word about which many people have differing definitions seeing as it has been in use since Plato’s times. One thing I still do not understand, however, is how the study of rhetoric could have been “at odds with religion, philosophy, and science at times”, as Herrick states. Even in medieval times when religion often opposed philosophy and science, I do not see how studying language and its “means and meaning” could disagree with any of the three fields listed.