ALL philanthropists want their donations to mean something, be it for a new wing for a hospital or to finance a program aimed at doing social good. Increasingly, though, philanthropists are looking for a way to measure the impact of their dollars.

There is certainly a lot of interest in impact investing — essentially investing money in an organization, either profit-making or nonprofit, with the expectation that it will generate a social benefit and perhaps a financial return. But people who embrace impact investing as the future of serious philanthropy often seem to me like scolds. Shouldn’t people be able to give away their money however they want?

Sure, you get a tax break for making a charitable donation, and some advisers to philanthropists argue this means you have a responsibility to give your money away wisely. The same could hold true for people making smaller donations.

Still, I had an interest in understanding impact investing better and was eager to sit down with Matt Bannick, managing partner of the Omidyar Network, an organization started by the founder of eBay that makes grants and investments in groups focused on economic and social change.