Is it the character or the play? That is a famous question regarding storytelling: What drives the story, indeed what makes it a good story?

The same question can be asked of impact investing: is it the specific social business or the broader social cause that makes a good investment?

Antony Bugg-Levine, the chief executive of Nonprofit Finance Fund, and a pioneer in the impact investing space as managing director of the Rockefeller Foundation, which spawned the Global Impact Investing Network, says it's better to focus on the social challenge, not the specific social enterprise. "If you ask, 'Where can I make an impact investment?' you will end up doing less interesting work then if you ask, 'What social challenges matter most and how can impact investing help to address them?'" he says in an editorial entitled, ''The Future of Impact Investing'' for Momentum, a journal published by Tides, an organization that provides myriad charitable donor services.

By example, Bugg-Levine writes, "In New York City in 2010, Nonprofit Finance Fund set up a loan pool for organizations such as soup kitchens and homeless shelters. But we found them too financially shaky to take on debt. If we were only looking for places to invest, we would have moved on to less risky borrowers. But because preserving New York's safety net is crucial, we didn't give up on this effort. So we set out to build the Community Resilience Fund to support 100 agencies' transition to more sustainable business models. This fund would not be possible without impact investors offering millions of dollars in loans. It also requires substantial grant support from private donors and credit enhancement from City Hall. This is the approach that will enable that New York City domestic violence agency to survive."

In short, by looking at solutions to social challenges at large, new approaches can be found that may not exactly fit the business mission of any one, or even pool of social enterprises. This is also why collaboration is key among impact investors. "Collaboration will be central as impact investors work with governments and donors to tackle challenges that no one can tackle alone," Bugg-Levine writes.

I agree. Getting hung up on individual businesses detracts from serious solutions to social problems. Willy-nilly investing in businesses for profit is one thing (basic, fundamental analysis could take investors in all sorts of business sectors). But when it comes to addressing an issue, an investment policy and plan are de rigueur.

To be sure, there may be plenty of businesses to invest in to tackle a social cause, and one should stick to those best in class. Straying outside this mandate brings trouble.

"We are going to need to mobilize billions of impact investing dollars to secure a just and vibrant future. Fortunately, the impact investing movement has expanded the arena in which for-profit investment is recognized as a morally legitimate and economically effective tool to promote social justice. Now we need impact investors to be worthy of our times and operate with the insight and sophistication necessary to capture this movement's potential," Bugg-Levine writes.

That means sticking to plan to find solutions to a broader cause.