For thirty years, I have made my living as a writer. Perhaps not in the way you’d imagine. It was certainly never what I imagined.

I’ve been a copywriter for my entire career. I’ve made a great living writing advertising and marketing materials—sometimes educational materials and museum exhibits, occasionally something a little more commercial, a handful of ghostwriting jobs. I’ve written everything from speeches for big corporate executives to magazine ads for liquid manure systems, packaging copy for Fruit of the Loom underpants to TV commercials for governors and U.S. Senators. I have been paid pretty highly to convince people to buy stuff. So you’d better believe I understand the power of words.

Words can convince people they simply have to have stuff they don’t need. Words can convince people they’re superior to someone who goes to a different church or whose skin is a different color. Words can convince people that certain of their neighbors aren’t fit to live.

Words have been responsible for myriad bad things humans have done to each other since the first caveman grunted out a lie. Words can turn sensible people into mindless automatons. Words can hurt and words can kill.

I’m not equating my copywriting career with genocide. On the contrary: I have always believed in my work. I have worked for wonderful people in outstanding companies and not-for-profit organizations. I know the power of words to attract people to great products and causes. I believe every word I write—otherwise, I couldn’t get up in the morning.

Words can also alert people to grave injustice. Words can illuminate hatred and prejudice and inequality. Words can inspire others to acts of valor and selflessness. Words can challenge people to take up the fight against things they think are wrong—or spread good throughout the world. Words are the most power tools human beings ever invented—the pen is, indeed, mightier than the sword, because no one would ever wield the sword without the pen first fomenting anger or outrage or greed.

Think about that: language is the most powerful invention in the history of the human race. And, as a writer, you’re in charge of the words. Please use them responsibly.

But not necessarily cautiously. While you have to be clear about the words you write, you also have to be passionate. If you are trying to change the world with your writing, you can’t hold back. At least not when you’re sitting down to write your first draft. It’s the place to let everything spill out of your heart and onto the page—every bit of love and honor and outrage you have in your heart. You can go back later and make sure it all makes sense.

You’d better believe what you write, too. Writing is simply too difficult a task write stuff you don’t believe. If you can actually write lies in the first place, they will come back to haunt you in the form of stomachaches and guilt. Writing for the wrong reason will suck the life right out of you.

“Money” is a great reason to write. But it can’t be the only reason. Even when you’re writing for money, you have a responsibility to the truth.

And, these days, writing for money is harder than ever before. The traditional publishing industry is withering. Daily newspapers are shrinking. Magazines–lord. Has anyone picked up Newsweek recently? The ubiquity of “free” words on the Internet has made it more difficult to make a living with your writing.

More difficult. But it also means that clear, true, passionate writing is even more essential. Your words can reach a wider audience, easier than ever before–but only if they can cut through all the tweets and Facebook updates and blogs and ads everything else out there competing for attention.

Your words are more important than ever. Choose them with passion and precision. Believe what you write. You’re working with the most powerful stuff known to humankind. You have the power to change the world.