What Do You Mean by “System?”

Describing systems thinking requires that we first define “system”. Despite the commonness of the word, system, defining it proves neither easy nor obvious. In almost every systems thinking workshop we have participated in participants, when asked to define it, at first feel very confident that they can define the word. Then, when asked to independently write it out, they get frustrated, eventually feeling as if the word includes so much that it does not define anything. There are many different definitions of “system” in the literature but they are more alike than different and it does in fact carry a very precise meaning.

Answer the following:

Question 1:

The left-hand column of this table lists a couple of entities that satisfy a criterion. That is, both an automobile and a compost pile get a “Yes” when we ask whether they incorporate this criterion. The entities on the right column fail to satisfy that criterion. They get a “No.”

The question: What is the criterion that these entities pass or don’t pass?

Before moving forward, please take the time to hazard some guesses. Click hints for help.
Hint # 1

Hint # 2

The Answer:
A Stack of baseball cards represent a collection of items that do not interact with each other. While the stack can include players from the 50’s, players from the Yankees, etc., the cards themselves do not tie to other cards in an active way.

Likewise the inert rock pile, as it represents a collection of pebbles, schist, sedimentary stones, etc that do not interact with each other.

By contrast the elements of a compost pile — organic matter, minerals, water, and microorganisms interact with oxygen and each other to gradually transform the compost pile into finished rich compost for the garden.

In the same way the car consists of parts such as a driveshaft, motor, differential, wheels and cabin that interrelate together to provide transportation to the driver.

The criterion:
Does this entity represent a system of interconnected and interacting parts that together provide some function?

The exercise points to some defining properties of a system.

  1. First, it evokes the fact that a system functions. That is, a system delivers on a specific purpose / function. Compost piles transform vegetative waste into rich usable humus soil. Cars transport people.
  2. Second, the exercise evokes the fact that each part in the set can affect the behavior of the whole system. That is, you need wheels and a motor for the car to work. Compost piles need the right amounts of oxygen, water and microorganisms to deliver finished compost. Cars do need a gas pedal which in turn connects with a fuel injector which in turn feeds cylinders that contain sparked explosions, etc.

By contrast rock piles do not DO anything. They can sit in the way of things but they of themselves do not do anything. Another person may organize a stack of baseball cards but the cards themselves do not interrelate to deliver a defined function.

Then we can refine our understanding with another exercise. Try this Question.

Question #2

As with question 1, identify the question or a criterion that generates these ‘yes’s and ‘no’s for these items.

Hint 1

Hint 2



The Answer
A car can transport people without sun visors and glove compartments but not without an engine of some sort and a drive shaft. The point: a system consists of essential parts that together allow it to perform a defining function.

Does the system need these parts in order to deliver its function?

These examples help create the “mental model”  and logical rules that segregate systems from just collections of things.

Read more about how to recognize systems here.

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