To design sustainable human communities, we first need to understand how nature sustains and promotes life. By studying the long history of human evolution, we realize that sustainability is not an individual attribute but an element of an entire web of relationships, as it always involves an entire community. This is the deeper lesson we are called to learn from nature. The way to sustain life is to build and support communities. The principles for designing our future social institutions must align with the organizational principles that nature has evolved to maintain the web of life. A unified epistemological framework for understanding material and social structures will be essential for this task. The purpose of this book is to offer an initial outline of such a framework.