The SiD Sustainability Definition

This is the core unit of the entire course. Everything before it sets the stage. Everything after it builds on what you learn here. The Symbiosis in Development definition of sustainability is precise, testable, and every word earns its place.

Sustainability is a state of a complex, dynamic system. In this state, a system can continue to flourish resiliently, in harmony, without requiring inputs from outside its system boundaries.

Applied to our civilization, this state is consistent with societies powered by renewable energy and closed-loop material systems, living in thriving ecosystems, on a biodiverse planet, with healthy and happy individuals living in just, tolerant, and diverse cultures, supported by open and transparent economies.

Two sentences. Let us unpack every word.

"State": Reconfiguration, Not New Stuff

Consider a light switch. It is in the "on" state or the "off" state. The switch consists of the same materials either way. Nothing is added or removed. It just changed state.

This is the first critical insight of the definition. Sustainability is not a physical property of material objects. It is a configuration of a system. One system can be in a state of sustainability while another is not, even though they consist of exactly the same components.

What does this mean in practice? We can reach a sustainable society with everything we already have. We do not need any extra stuff. We need to reconfigure the relationships between us, our stuff, and each other. We could have been in a sustainable state in the past (and perhaps we were). We can achieve it in the future. But we are not there today, and getting there is not easy, because we departed this state probably a few hundred years ago.

"Sustainability Is Not a Property of Objects"

Consider a toothbrush that says "sustainable" on its package. What does that mean? Is it made from environmentally friendly material? Produced without forced labor? Does it promote a sustainable lifestyle?

Think about its impact on society. That impact differs depending on whether it is used daily with a lot of water or very little. Whether its production involved toxins dumped in a river. Where it was made, how it was transported. What will happen when it wears out: incinerated, recycled, or lost in the ocean?

The "sustainability" of the toothbrush depends on factors outside the toothbrush itself, some of which have not yet happened. Because the product does not carry within itself the control to define how it is made, used, or discarded, you cannot say much about its "sustainability" from the object alone.

This leads to a critical realization: an object cannot be called sustainable without knowing the answers to these questions. Saying a toothbrush is "sustainable" is like saying a person is "love." It is simply nonsensical. We do not care about an eternally existing toothbrush. We care about all the relations of the toothbrush with things that matter: the environment, people, your life, society. Sustainability is not a physical property of material objects. It is expressed on the system level.

The Love Analogy

It is a bit like the word "love." A car does not love, nor does a house or a single person in isolation. Love is an expression of a bond between things. It requires a relationship. It exists between entities, not inside them.

Just so with sustainability. It is relational. It lives in the connections, the flows, the dependencies, not in the objects themselves.

"Complex" Means Non-Linear and Emergent

The word "complex" underlines that we are talking about systems understood as non-linear, infinitely intricate entities, almost like biological organisms, not predictable mechanistic machines. Complex systems exhibit behavior that cannot be predicted using normal mechanical analysis.

The weather is an easy example: nobody can accurately predict it more than a week out. Just as our brains are more than a sum of molecules, complex systems are more than the sum of their parts. They tend to behave less like machines and more like creatures displaying "emergent" behavior. Acting on one aspect in isolation will always produce side effects on the rest. Expecting them to respond like machines is a one-way road to disaster.

"Dynamic" Means Always Moving

The definition describes sustainability as a state of a dynamic system. This means sustainability is an edge condition of something that always moves, changes, grows, shrinks, and acts in accordance with changes in its environment and internal composition. A system can move and change while still remaining in the state of sustainability, as long as it does not cross the border of its state.

This is important. Sustainability does not mean freezing the current state or stopping change. It means the system can continue to change, adapt, and flourish within a healthy range.

Nothing is eternal, and nothing should be. A sustainable system "pulses" like all natural systems do, aiming to adapt itself to be better-fitted each time around. A sustainable system also inherently accepts there is an end to things, and gracefully resolves itself when that moment arrives. Like dead trees in a forest becoming new habitats for other organisms, leaving room for the cycle of life to continue.

Three Properties: Resilience, Autonomy, Harmony (RAH)

The second sentence of the definition identifies what the sustainable state actually is. It breaks into three terms:

1. Resilience: the degree to which a system can survive unexpected occurrences. A critical part of continuing to exist. If something unexpected happens and the system breaks, it was not resilient enough to be sustainable.
2. Autonomy: the degree to which a system can take care of its own needs and continue doing so. Captured in "without requiring inputs from outside its system boundaries." A system that depends entirely on external inputs is vulnerable.
3. Harmony: the degree to which a system's agents coexist justly and equitably. Inharmonious systems, with unjust distribution of resources and power, give rise to internal strife and war. A system can be resilient and autonomous, but without harmony it will collapse from internal tension. (A system that is resilient and autonomous but not harmonious conjures images of hardy evil empires impossible to overthrow. That is the opposite of what we hope to achieve.)

These three influence each other. Increased autonomy can decrease resilience (an isolated village that does not invest in trade relationships). If everyone can be autonomous, there is more harmony. The interplay matters as much as the individual components.

The word "flourish" is present too. Resilient, self-sustained, harmonious life is already great, but there is value in excitement and beauty as well. Flourishing means more than just surviving.

How Does It Add Up?

A sustainable system is self-sufficient, resilient enough to continue operating under a wide range of expected and unexpected events, and harmonious and just while it flourishes. Translated to modern society: closed energy and material loops, no reliance on finite resources, ethical distribution of wealth and power, thriving ecosystems and fellow species, equitable access to a life of quality, and open, transparent economies.

"When we try to pick out anything by itself, we find it hitched to everything else in the Universe."

John Muir