Rhetoric is one of the three original liberal arts or trivium (the other members are sex education and potty training) in Western culture. In ancient and medieval times, the rhetor was usually some rich bastard that owned land, so they let him do whatever the hell he wanted to. This involved standing out in the open air spreading his bullshit to anyone that passed by. As such, rhetoric is said to flourish in capitalistic societies with rights of free speech for those that have the cash to back it up. But if you are poor or belong to a minority group, you better be able to run fast if you want to try the practice of rhetoric, because when the police show up it is time to book.
The concept of rhetoric has shifted some over time. Today rhetoric is usually used in a negative context, meaning "particularly offensive bullshit," which is pretty inaccurate considering that it is just like any other "tool" and that its valence depends upon the user. However, it is not uncommon to hear phrases like "Ted Kennedy gave a speech today while downing three buckets of fried chicken and farting on an intern that consisted primarily of empty rhetoric."
People who study rhetoric today are usually losers who couldn't do anything else right when they were in high school so they joined the forensics or debate team. They were nerds but they didn't know how to play chess so they thought that by becoming bullshitters they could show off their intelligence and avoid getting beaten to a pulp on the football field. Well, it was all okay, except no one came to watch the geeks competing, so if you won first place in a rhetorical competition no one gave a shit and thus the loser went to college, studied 10 years, got a Ph.D in rhetoric and now works as an assistant professor at your local community college earning about 30K a year and voting for Democrats.
Socrates was a homosexual genius who said rhetoric meant speaking truthfully and earnestly. That lasted about a year until his student Pluto came along and really screwed things up by introducing an ethical discussion about it all that his own little boyfriend Aristotle totally blew to hell by inventing the first lawyer that was known back then as a Sophist, which in its third Latin declension pre-conceived means "Cocksucker that wants money for nothing." Basically, these guys begat every friggin' thing the white man studies today, and a lot started with their rhetoric bullshit as well as orgy time in the Parthenon.
Cicero was another gay guy that basically stole everything that Aristotle did but just changed the names around kind of like that mythology where Zeus becomes Jupiter and Venus becomes Aprhrodite and such. Then there was this guy named Quintilian that was illiterate so he invented the first comic strip and introduced the idea of the pictogram which meant that any illiterate reprobate could bullshit and call themselves a rhetorical expert which has led to most of our speech analysts today.
Rhetoric from the Renaissance
People were too busy smoking marijuana and painting dirty pictures to listen to anyone bullshit during the renaissance so there was no real development during that time. Some guys wrote some plays and stuff, but mainly these were just ways to get their rocks off and to write about sex in an artistic manner so that 20th century school boards would have something to fight about centuries later.
Some really weird shit has come to the forefront as post-modern rhetoricians have developed the idea that no matter what kind of bullshit you spread, you could make a lot more money if you convinced someone that it was going to get them in trouble with the Affirmative Action board if they didn't recognize it as true rhetoric. This began with classifying rhetoric by the rhetor, such as feminist, race, and interstellar forms.
Current state of rhetorical study
Rhetorical theory today pretty much sucks. It includes everything everyone has ever said being taken out of context and labeled as meaningful. It is forced on those freshmen who have to take that public speaking class that no one ever wants to. It also creates jobs for those geeks we talked about back in paragraph four. These "rhetorical scholars" meet at conferences such as the National Communication Association conference where they spend tons of money on lavish hotel rooms where they get drunk out of their minds and cheat on their spouses. They publish research in journals that no one reads and convince each other that they are pretty important.