What do public benefit, performance metrics and evolution all have in common? No, it is not just the tendency of some to dismiss them all as ‘merely theories’. It is that they all rely on diversity to thrive. Whether you are looking at the provision of social services in Britain, the arts community in Berlin, or affordable housing in Boston, you will find a mix of non-profit organizations, government agencies and private companies providing the benefits. With regard to performance metrics and measures of impact, we have seen an explosion of indices for corporate social responsibility, social return on investment, and double bottom line accounting. And, of course, evolution is inherently linked to biological diversity, which is itself a lynchpin of a healthy region, ecosystem, and, ultimately, planet.

It is ironic, then, that one of the most consistent challenges to developing meaningful outcome or performance measures in the social sector is the old canard that ‘there are too many definitions of success’. In other words, success is too diverse to be measured by any common standards. Critics of measurement efforts will argue that some of the social sector is focused on school choice programmes, while others are trying to expand public investment in public schools. These entities are working at cross-purposes – how can there be one definition of success?