Gall's Law

What is it?

Gall’s Law states that a complex system that works is invariably found to have evolved from a simple system that worked.

Simple Examples
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Gall’s Law says that if you want something complicated to work well, you should first build a simple version that works. Then, improve and expand it step by step. If you try to create the full complicated version from the start, it will almost always fail.

Simple Examples

Building a house 🏠 You don’t start with a mansion. You first build a small structure (like a single room or cabin). Once you know it stands strong, you can add more rooms, floors, and decorations. If you tried to build a massive mansion in one go without testing, it might collapse.
Apps or software 📱 Successful apps usually start with a small minimum viable product (MVP). For example, Facebook started as a simple site just for Harvard students. Only after it worked well did it grow into today’s massive platform.
Airplanes ✈️ The Wright brothers didn’t build a jumbo jet right away. They built a simple glider first, learned from it, then made powered planes, and eventually aviation evolved into modern airliners.

👉 The idea: Start small, make sure it works, then grow.

Gall’s Law states: A complex system that works is invariably found to have evolved from a simple system that worked.

This principle highlights the evolutionary nature of functional systems, whether in engineering, biology, or organizations. It implies that successful complexity emerges incrementally, not from top-down design.

Connections to Other Principles

Evolutionary Biology (Darwin’s Principle) 🧬 Just as organisms evolve gradually from simpler life forms, successful systems adapt over time. Attempting to design a fully formed "complex organism" from scratch is unrealistic.
- Example: The human eye evolved through many intermediate stages, each functional on its own.
Software Engineering (YAGNI & MVP) 💻 In Agile development, the Minimum Viable Product (MVP) embodies Gall’s Law: start with the smallest thing that works, then iterate. Similarly, You Aren’t Gonna Need It (YAGNI) warns against building complex features prematurely.
Systems Theory 🔄 Complex adaptive systems (like ecosystems or economies) can only emerge from simpler, stable components. Designing complexity directly often results in fragility or failure.
Cybernetics & Control Theory ⚙️ Stable control systems (e.g., thermostats, autopilots) are first built with basic feedback loops. Adding complexity without proven stability usually destabilizes the system.
Conway’s Law 🏢 Systems reflect the structure of the organizations that design them. When organizations grow organically, their systems evolve in complexity—mirroring Gall’s principle of stepwise development.

Key Insight

Gall’s Law teaches that functional complexity must be grown, not designed whole. It is less about minimalism and more about iterative evolution: each step must produce a working, coherent whole.

References