"Reality is made up of circles, but we see straight lines.”
Peter Senge

A system is multiple elements where each element affects the whole, the way each element affects the whole depends on one or more other elements, and no effects are independent. When you take it apart, the parts stop working.

Lots of things are systems. Cars, organisms, cities.

Systems are complex, not complicated. The output is discontinuous with the input: You don’t get out what you put in. Each system is capable of doing something that none of its individual parts can.


Russ Ackoff. If Russ Ackoff Had given a TED Talk

A system is a whole made up of parts, each of which affects the system’s behaviors or properties, and each of which’s effects is dependent on one or more of the other parts.

A system is a whole that cannot be divided into parts. That system is defined by properties or capabilities which none of its parts have. When a system is taken apart, it’s no longer a system. A system is not the sum of its parts but the product of their interactions.

Russ Ackoff. U.S. Navy Two Day Training in Thinking, Understanding, and Learning .

A system is two or more elements that satisfies three conditions

  1. Each element can affect the whole.
  2. The way each element affects the whole depends on at least one other element.
  3. If you group any set of elements, they’ll have an effect on the whole, but none of them have an independent effect. A system is a whole that cannot be divided into independent parts.

When a system’s parts don’t fit, it doesn’t make it something else; a poorly constructed automobile isn’t a bicycle. Changes in a system that maintain fit can make it something else; a mousetrap with parts removed no longer functions as a mousetrap, but it works as a tie clip, provided you are more invested in making a point than being in fashion.