Everyone seems to have his or her own definition. Some people even suggest it's more profitable to let a thousand flowers bloom than to try to pin down the definitive definition.
But when one of the pioneers of the profession offers his thoughts, it's worth noting. So I was thrilled when Harold offered some additional context in an email.
He added what he called one "nit," pointing out that he considers PR an applied social science. I've already corrected my original posting to reflect that addition. But the significance of planting PR in the realm of applied social science is worth considering.
As Harold put it, PR "is an amalgam of behavioral psychology, cultural anthropology, sociology, history and geography.The net/net is that the objective of public relations is persuasion, whether it's to want someone to sign up with AT&T rather than Verizon, vacation in Greece rather than Brazil, elect Candidate A over Candidate B. Nor is it a modern addition to the behavioral landscape: people unknowingly practiced public relations (using clubs or spears) while they still lived in caves. I believe it is endemic to the life cycle."
So if you know someone studying PR in college, make sure their course load includes a heavy dose of those disciplines (save club and spear-wielding). They'll learn how to write news releases (if there still are such things) when they graduate.