I have mentioned on many occasions that my first job was to teach science in public schools.
The one thing that teaching science imbues you with is a high regard for the difference between a fact and an opinion.
In science, establishing something as a fact is a daunting process. First you need convincing experimental data. Then you need to establish the reliability of your data by repeating the experiment several times and getting the same results. Then other scientists will "peer review" your experiment by trying to duplicate the results. Or, more likely, by trying to disprove your results.
Science doesn't just accept something as a fact because someone with a big name, a chest full of medals, or a fancy title says so. Even after a hundred years, scientists are still questioning and testing Einstein's ideas about gravity and the speed of light.
The world of advertising and marketing couldn't be more different. If enough loudmouths say the same thing enough times at industry conferences or in trade magazines, facts are born. These "facts" are rarely if ever validated and they are often repeated ad nauseum in meetings and conference rooms.
While in most fields there is a great gap between an opinion and a fact, in advertising and marketing a "fact" is usually just the elongated shadow of some blowhard's opinion.
The result of this is that we have an industry without reliable principles. We have trendy "solutions" that blow with the wind. We have charlatans successfully masquerading as experts. We have a vocabulary of dreadful jargon that passes for insight. We have a class of leaders called "CMOs" who can't seem to hold a job. We have ad industry titans who have never actually practiced the art.
Our industry has reached such a level of effete confusion that making a self-evident statement like "the purpose of advertising is to sell something" is now controversial, and can get you into a heated argument.
Frankly, in the current environment, I don't know how anyone in our industry who can think straight can be anything but a contrarian.