Systems have purpose. As we saw in the examples above, every system has some purpose that defines it as a discrete entity and that provides a kind of integrity that holds it together. The purpose, however, is a property of the system as a whole and not of any of the parts. For example, the purpose of an automobile is to provide a means to take people and things from one place to another. This purpose is a property of the automobile as a whole and cannot be detected in just the wheels, the engine, or any other part.

 

    All parts must be present for a system to carry out its purpose optimally. If you can take pieces away from something without affecting its functioning, then you have a collection of parts, not a system. In the toolbox example, if you remove a wrench, you have fewer tools, but you have not changed the nature of what is in the box. Likewise, if you can add pieces to a collection without affecting its functioning, it’s still just a collection.

 

   The order in which the parts are arranged affects the performance of a system. If the components of a collection can be combined in any random order, then they do not make up a system. In our toolbox, it doesn’t matter whether the screwdrivers are piled on top or buried at the bottom of the box (unless, of course, you really need a screwdriver now!). In a system, however, the arrangement of all the parts matters a great deal. (Imagine trying to randomly rearrange the parts in your automobile!)

 

    Systems attempt to maintain stability through feedback. In simplest terms, feedback is the transmission and return of information. The most important feature of feedback is that it provides information to the system that lets it know how it is doing relative to some desired state. For example, the normal human body temperature is 98.6 degrees Fahrenheit. If you go for a run, the exertion warms your body beyond that desired temperature. This change activates your sweat glands until the cooling effect of the perspiration readjusts your temperature back to the norm. Or, in our car example, imagine that you are steering your car into a curve. If you turn too sharply, you receive feedback in the form of visual cues and internal sensations that you are turning too much for the speed at which you’re traveling. You then make adjustments to correct the degree of your turn or alter your speed, or some combination of both. If you are a passenger in a car driven by someone who is not paying attention to such feedback, you might be better off getting a ride with someone else!