George Overholser is another "alpha dog" thought leader in the world of philanthropy. He is a founder of the Nonprofit Finance Fund, co-founder of Third Sector Capital Partners, and is generally a superior example of the human species. I was fortunate enough to have caught a presentation of his back in 2009, and my ideas about philanthropy have never been the same since. Basically, George challenges us to distinguish  "equity-like" and "revenue-like" investments in the social sector. His report Nonprofit Growth Capital is seminal and absolutely required reading.