The TED conference teased its audience with a "surprise guest" and they lived up to the billing. When Pope Francis took to the TED stage (remotely from his humble guest house in Vatican City), it lit up social media. But while the appearance might be surprising, the approach Francis took to writing his message isn't a surprise to those who study the art of persuasion.

Francis is a fan of using a rhetorical device called the "Rule of Three." It pervades the Bible as well as great speeches and literature throughout history.

Pope Francis learned the rule in his Jesuit training as a fundamental guideline to writing and delivering persuasive speeches. In his first homily as the newly elected pontiff, Francis summed up his faith in three bullet points: journeying, building, and professing. He even joked about it once saying, "First of all, I will talk about three things: one, two, three, like old-timer Jesuits used to do, right? One, two, three!"

In his talk at TED 2017, Francis divided his message into three key points and, like putting a yellow highlighter to paper, he flagged the messages verbally.

Key message #1: Everyone is connected. "First and foremost, I would love it if this meeting could help to remind us that we all need each other, none of us is an island."

Key message #2: Social inclusion. "This brings me to my second message. How wonderful would it be if the growth of scientific and technological innovation would come along with more equality and social inclusion..."

Key message #3: Tenderness. "The third message I would like to share today is, indeed, about revolution: the revolution of tenderness. And what is tenderness? It is the love that comes close and becomes real."

Throughout the script Francis also grouped sub-ideas into three. For example,

"Love does require a creative, concrete and ingenious attitude."

"In order to do good, we need memory, we need courage and we need creativity."

Francis is most effective as a communicator when he combines the rule of three with another powerful rhetorical device, anaphora (starting successive sentences with the same word or phrase):

Hope is the virtue of a heart that doesn't lock itself into darkness...

Hope is the door that opens onto the future.

Hope is a humble, hidden seed of life that, with time, will develop into a large tree."

The rule of three simply means that most people can only remember about three or four points in short term or 'working memory.' Think about it. How do you memorize a telephone number? If you're like most people, you group the longer 7-digit number into chunks of three and four.

In literature and writing, there's a reason why Thomas Jefferson focused on three unalienable rights in the Declaration of Independence (life, liberty and the pursuit of happiness). There's a reason why, as children, we read stories about the three bears, the three little pigs, the three Musketeers and the three ghosts who visit Ebenezer Scrooge. The rule of three is a fundamental building block of persuasion and is used in famous literature, public-speaking, and even movies which often follow a 3-act structure.

The next time you're preparing a pitch or presentation, stick to three points.

Give a customer three features of your product. Offer a recruiter three reasons to hire you. Provide your team with three specific action items.

The rule of three. It works for Pope Francis. It will work for you.