Much of what I learned in high school was most effective at setting one up for a lifetime of therapy. But there were a few gems here and there that have managed to stay with me throughout the ensuing years. One of those was the difference between facts and opinions. Several of my teachers devoted many class periods to helping their charges grasp what separates the two.

It’s a lesson that seems to be lost on many people, who develop their own opinions about something and then state those opinions as though they were factual knowledge. While the most obvious examples are those modern-day idea marketplaces — talk radio, cable news channels, and online forums — I’ve also seen the trend drift into the ways in which companies promote themselves or their beliefs.

I’ve encountered many situations in which a company official asks me to take his or her opinion and present it as fact on a website, in a brochure, or in an article. And when I try to gently point out that it’s not quite factual, I usually get a very steely look in return.

As you’re developing your own materials, make sure you remember the distinction between opinion and knowledge, and present each accordingly.