There is a growing recognition that the next era of social sector innovation is emerging in what The Bridgespan Group's Jeff Bradach and Abe Grindle call transformative scale. This innovation will require that we not only act differently, but also think differently.

To start, we need to shift our thinking about scale itself. The existing mental model of scale is left over from the industrial era. The 20th century was an era of mass production in which scale meant the ability to produce and deliver large quantities of goods and services. But the 21st century is an era of mass collaboration. Scale is no longer about production but impact. It's not about how big you are and how efficiently you operate. It's about how well you catalyze action around a shared purpose.

When the landscape changes, our mental models become outdated. Transformative scale will require that we adopt new mental models in four important areas:

1. Strategy: Product to Platform

In a digital age, the value of one's product is less important than the value of one's platform. It's not about how well you create value, but how well you enable and empower others to create value. For example, as products, Microsoft's smartphones are arguably just as good as those from Apple and phones using Android, but as a platform, Microsoft's phones fall short. Developers are less likely to build apps for them, and the overall ecosystem is less appealing to customers. Meanwhile, in areas like software, transportation, and hospitality, platform companies like Salesforce.com, Uber and Airbnb demonstrate the power of platforms to disrupt even well-established industries.

2. Organization: Hierarchy to Network

The traditional approach to organization is hierarchical, with specialized roles and formal reporting structures. Industrial-era scale was achieved through centralized control and decentralized operations. This approach is efficient and consistent, but rigid and monolithic. Transformative scale requires greater agility and adaptability, and therefore a different organizational model. Networks are the answer. We can see the power of networks in everything from social media to the design of the Internet. Even in nature, flocks of birds and schools of fish can move with remarkable coordination, and yet no one is in charge. Network principles guide their behavior.

3. Communication: Audience to Community

For the last hundred years, communication has been largely one-to-many through broadcast media. Now the digital revolution has enabled many-to-many communication, enabling people to communicate on a global scale. Once-passive audiences are becoming collaborative communities. Social media such as Facebook and Twitter are only the tip of the iceberg. There is an opportunity for social innovators to create and engage their own communities in the way that Nike has engaged runners through its Nike+ community and American Express has engaged small business owners through its Open Forum community.

4. Relationship: Consume to Co-create

Connectivity and empowerment are changing the relationship between individuals and institutions. People are no longer consumers but co-creators. They don't just want to receive something already made; they want to participate in its creation. This applies to every type of stakeholder—not just customers, but also employees, recipients, donors, and volunteers. Co-creation generates better engagement and ownership, as well as more creative and enduring outcomes. The success of companies like Kickstarter, Quirky, and Threadless are useful role models for those in the social sector.

To understand the creative outcomes of these shifts, consider the organization Ushahidi, which received the 2013 MacArthur Award for Creative & Effective Institutions. Ushahidi, which means "bearing witness" in Swahili, has brought transformative scale to transparency in human rights abuses and emergency response for natural disasters such as the 2010 Haiti earthquake. The Ushahidi software platform enables people to report incidents of abuse and emergency needs in their communities, mobilizing a rapid-response network. The combination of platform, network, community, and co-creation is a marked contrast to the more traditional approach of centralized collection, reporting, and outreach.

We are entering a time in which transformative scale is not only possible, but also essential. New challenges require new thinking. Across both the commercial and social sectors, we can see new ways of creating value, organizing, engaging, and collaborating around a shared purpose. With a shift in thinking, we have the potential to unleash the imagination, energy, and resources of a global community of citizen transformers.

Mark Bonchek is the founder of the SHIFT Academy, whose mission is to update leaders' thinking for the 21st century, and thinkORBIT, a consultancy that helps clients create new models of engagement for a digital and social age.