Complex systems emerge when four conditions are met: sufficient interacting parts, local autonomy, negative feedback loops, and limited randomness. These universal rules explain how order arises from disorder across all scales, from atoms to societies.
Book: Notes on Complexity
What makes a city, a cell, and a galaxy similar?
Neil Theise explores complexity theory as a framework for understanding how order and structure arise in nature. He investigates how systems, either biological, physical, or social, self-organize.
He identifies four universal conditions that allow complexity to emerge:
Sufficient numbers of interacting parts: Too few elements yield randomness, while enough parts enable patterns. For example:
- A single ant's behavior is simple, but thousands together form efficient networks that find food, regulate temperature, and adapt to change.
- One neuron in our brain just fires or rests, but billions interacting create thought, memory, and consciousness.
- Individual buyers and sellers make local decisions, but together they generate price systems and economic trends.
Local autonomy: Each component acts based on local information rather than global control. For example:
- Each white blood cell acts on local information, attacking pathogens it encounters without central command, but the overall immune response remains coordinated.
- Drivers make decisions based on nearby cars, not the entire system, but traffic patterns, such as waves, jams, or free flow, emerge.
- Individual developers contribute to open-source software autonomously, following shared protocols, and complex platforms evolve organically.
Negative feedback loops: Systems self-correct by abandoning unproductive paths. For example
- When you overheat, you sweat. When you're cold, you shiver. The body self-corrects to maintain homeostasis.
- If rabbits multiply, foxes thrive. Too many foxes reduce rabbits, which then reduces the fox population again. Populations stabilize through feedback.
- Advancing prices can suppress demand, which lowers prices again. Feedback loops stabilize markets (until they're disrupted).
Limited randomness: Systems require both constraint and flexibility. For example:
- Random genetic mutations introduce novelty, but natural selection constrains which survive. That balance drives evolution.
- A jazz band maintains a shared rhythm and key, but allows for spontaneous variation. The mix of order and freedom in artistic improvisation produces creativity.
- Startups experiment (randomness) within structured markets and regulations (constraints), oftentimes leading to more innovation.
These rules apply everywhere: from cells to cities. When systems fail to meet these conditions, they become dysfunctional. For example, modern hierarchical organizations often violate local autonomy. When every decision flows through a central authority, the system becomes brittle.
This is also highly related to Antifragile.