You may have heard the phrase “pay it forward,” and even if that’s all you’ve heard, you probably get the concept. Something was given to you, and instead of paying for it backward by giving the giver money, or even doing something for them, you go forward, extending the kindness to another.

The phrase was made popular by the 1999 novel Pay It Forward by Catherine Ryan Hyde, which was made into a film in 2000.

The story of the novel’s writing began when Catherine was driving through a rough neighborhood, and all of a sudden her vehicle caught on fire. Two strangers arrived to help her, then disappeared. The incident sparked an idea that became a nationally best-selling story.

The novel tells the story of Trevor McKinney, a seventh-grader who is given an assignment by his social studies teacher: devise and put into action a plan that will change the world for the better.

Trevor comes up with a simple plan: create a viral charitable movement that networks good deeds out from one another. “Pay It Forward.”

The plan begins by doing a good deed for three people. Each of those people, in turn, must do another favor for three other people. The favor done must be a large one, a deed that the person cannot perform on their own. It can’t be, for example, fetching a friend a snack or holding the door open for an able stranger.

Trevor’s task, for example (SPOILER ALERT), is to help a homeless man. His first deed fails. Trevor doesn’t give up. He tries again. He helps his own social studies teacher, then two more people. Unbeknownst to Trevor, one of the people he helps puts three other people in their will, giving them thousands of dollars.

I won’t spoil the ending, but Trevor is unaware that his deeds catch on and affect countless lives.

The famous fictional story is not such an original idea, as many people have tried to deliberately initiate such a charitable movement, creating an act of kindness that can move forward and grow. The novel itself even spurred many people to create such an initiative.

As the story admits, sometimes these efforts putter out. People forget about their role in the initiative. The pressure is too much. Or their failure defeats them. But kindness has a stubborn way of catching on.

Consider the math. If each of the three people you do a good deed for successfully does a good deed for three others, you triple your deed’s worth by one degree. 3 becomes 9 (well, technically 3 becomes 12, your 3 plus their 9, so we’ll just say your 3 inspires their 9). Keep the math going. If three more people are affected by each of those people, that’s 27 people reached. Keep going. After six rounds of paying it forward, as many as 729 people can be reached.

Especially with the advent of new communication technologies and social media, we have new opportunities to help spread kindness, along with the proof to show that it works.

For example, maybe you’ve heard of the Ice Bucket Challenge. Film yourself getting a bucket of ice poured on your head. Nominate three people to do the same. Pour the water on yourself and give a small amount of money to a charity. You can opt out of the ice water by giving more to charity, or some variation of that mechanism.

Weeks after the Ice Bucket Challenge began, the ALS Association reported over $41.8 million in donations from over 739,000 people in a single month! That is twice the amount they received in the entire previous year!

This principle is part of the motive behind Kindness Cards. Our campaign is to help make kindness viral again. Do something tangible, provide a tangible token of the goodness you passed on, inspire the other person pass it on, and watch the kindness grow like a germ.

Math works. If we put it into practice with kindness, math is working for kindness. If we are on the same journey, we operate on the same basic principles. Start the journey now, and there’s no telling where it will end up.