SSG understands sustainability as a process, rather than a static outcome. As such we seek human-driven solutions to today’s greatest challenges. We use sustainability as a lens to create an integrated and effective approach to addressing challenges including climate change, economic and social inequities, human health, ecosystem decline and sustainable community development. 

The figure on the right illustrates the economic, social and ecological dimensions. This concept of sustainability contrasts with the three legs of the stool approach which was based on the premise that the social, ecological and economic legs were equally important. The nested circle framework recognises that social and economic activity occurs within ecological limits. 

The idea of limits gives rise to the question of distribution. Should environmental resources be divided equally amongst the population of the earth? And if not, why not? What portion of the earth's resources should be reserved for other species? And what about future generations? These are the kinds of difficult questions that we seek to address using principles proposed by many wise people, for example:

• the Precautionary principle: "to keep every cog and wheel is the first precaution of intelligent tinkering". 
• Aldo Leopold's Land Ethic: "a thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise".
• Ghandi: "the world has enough for everyone's need but not everyone's greed". 

The comic below provides an overview of the development of the concept.