You know, I'm an English major, and I was NEVER treated to a course on Rhetoric. Later on, I was a law student for a short time, and there was no course on Rhetoric.
Why? For centuries, Rhetoric was one of the main subjects students paid to study. Why did they pay? Because it would help them to win debates and arguments. As critics have complained for centuries, the art of Rhetoric can be (and has been) twisted into making the worse appear the better cause.
But, like the two-edged sword it is, Rhetoric can make the better cause appear the only cause, and the best cause. Look to Churchill's war-time speeches, or to Lincoln's unforgettable "...that the government of the people, by the people, and for the people, shall not perish from the earth." You could paraphrase that, perhaps, as "the republican system of government must survive" --- and it's instantly forgettable.
Rhetoric is the ancient and very effective way to make your words STICK in the minds of other people. If you're at all curious about this subject, you probably want to read this book.
"If there remains in you a drop of curiosity, one drop of that quest for knowledge which makes great men stand out from their fellows, if there remains in you even the slightest glimmer of interest in learning how to speak and persuade others, I suggest that the solution is evident." :-) Jazzed it up a little, didn't I?