Jack Dorsey has given 15 million of his shares back to Square and he plans to give 40 million more - here's why

Jack Dorsey is the founder of Square, a payments company that filed to go public on Wednesday afternoon.

In the S-1's opening letter, Dorsey says he's given back 20% of his equity, or 15 million shares, to Square and a group he created, the Start Small Foundation, over the past two years. The organization, Dorsey says, meaningfully invests in small creative businesses and people, such as musicians and artists.

That's a lot of equity, but Dorsey says he's committed to giving back even more.

He intends to give up 40 million more shares, or 10% of the company, to invest in the effort to empower creative people and shops.

Why?

For one, Dorsey can afford it. He's a billionaire who also co-founded Twitter and is now CEO of that company too. But he also thinks Square will be a company that will have a major impact on the world.

"I believe so much in the potential of this company to drive positive impact in my lifetime," Dorsey writes. "I'd rather have a smaller part of something big than a bigger part of something small."