Ideas are the currency of the twenty-first century. The ability to persuade, to change hearts and minds, is perhaps the single greatest skill that will give you a competitive edge in the knowledge economy — an age where ideas matter more than ever.

Some economists believe that persuasion is responsible for generating one-quarter or more of America’s total national income. As our economy has evolved from an agrarian to an industrial to a knowledge-based one, successful people in nearly every profession have become those capable of convincing others to take action on their ideas. Think about the role of persuasion in our daily lives:

• Entrepreneurs persuade investors to back their startups.
• Job candidates persuade recruiters to hire them.
• Politicians persuade people to vote for them.
• Leaders persuade employees to take specific plans of action.
• CEOs persuade analysts to write favorable reports about their companies.
• Salespeople persuade customers to choose their product over a competitor’s offering.

In short, persuasion is no longer a “soft skill”— it is a fundamental skill that can help you attract investors, sell products, build brands, inspire teams, and trigger movements. Persuasion is so important to billionaire Warren Buffett that the only diploma he proudly displays in his office is a public-speaking certificate from a Dale Carnegie course. He once told business students that improving their communication skills would boost their professional value by 50% — instantly.

Words and ideas created the modern world, and words and ideas have the potential to make you a star in your field, as long as you can persuade someone else to act on them. Following the tactics of one ancient Greek philosopher can help.

More than 2,000 years ago Aristotle outlined a formula on how to master the art of persuasion in his work Rhetoric. Many great communicators have used it throughout the ages to deliver some of the most influential speeches, presentations, and share their ideas with the world.

To become a master of persuasion yourself and successfully sell your own ideas, try using these five rhetorical devices that Aristotle identified in your next speech or presentation.

[Here’s the first.]

1) Ethos or “Character”

To me, ethos represents the part of a speech or presentation when your audience gains some insight into your credibility. Aristotle believed that if a speaker’s actions didn’t back their words, they would lose credibility, and ultimately, weaken their argument.

For example, in a now famous TED Talk on reforming the criminal justice system, Human Rights Attorney Bryan Stevenson begins, “I spend most of my time in jails, in prisons, on death row. I spend most of my time in very low-income communities in the projects and places where there’s a great deal of hopelessness.” You’ll notice that Stevenson does not list his degrees, accomplishments, and awards like he might on a résumé. Instead, he establishes his character for those in the audience who don’t know him. By doing so, he is building a sense of trust between himself and his listeners.

As humans, we are hardwired to search for reasons to trust another person, and we do so quickly. After all, our ancestors had an instant to determine whether a stranger was friend or foe. A simple reminder that you are committed to the welfare of others will build your credibility before you lay out your argument.