Gall’s Law

Gall’s law states that complex systems can only be the result of an evolutionary process, and not the result of a design from scratch:

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system.  – John Gall (1975, p.71)

A complex system evolves from simpler systems by adding successive deltas of complexity. The only way to build a complex a system is through iteration. That’s what evoluation is about.

Iterations enable us to get feedback, correct and improve the system. See what works and what doesn’t. Fix mistakes.

The system must be working after each iteration. You can add new features, as long as it refines the existing system and keeps it running.

A tadpole becomes a frog by developing its legs, then its arms, and finally shrinking its tail. The frog’s legs, arms and body aren’t developed individually and assembled at the end. That’s not how evolution works.


Also, you can not evolve everything at once, since in the meantime the system might not work. A tadpole develops its legs, then its arms, and finally shrink its tail. Each iteration needs focus.

Gall’s law is relieving. It’s OK to not be able to handle all the complexity at once. And it’s not only you–it’s everybody.

A complex system can not be built using only theory and first principles, because there will always be details of the environment that we were not aware of. The only way to make sure something will work is to test it for real. Practice trumps theory.

Obsessing with getting it right the first time is counter productive. Just start somewhere and iterate. Too much unknown blocks our creativity. But once we have something concrete, ideas to improve come easily.

The tadpole also teaches us a lesson here: it first develops a tail, which then disappears later on. The tail is a good idea in the water, but not so much on the ground. You will have to reinvent yourself occasionally.


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