1. A system is a dynamically interacting and interdependent group of members or components and their attributes, forming a whole. This means that a system must consist of two or more members or components; one thing is not to be considered a system unless it is composed of multiple interacting components. For example, when we speak of interpersonal systems, an individual person does not constitute a system, but in terms of living organisms composed of component parts, a human being is most definitely a system. That is, insofar as we discuss something as a system, we must by definition refer to it as a group of interdependent parts, but it all depends on our point of view.

• "Dynamically interacting" means that there is movement and change within a system. A static crystal such as a diamond is not considered a system because its parts do not move or change, although technically its subatomic particles are in motion.
• "Interdependent" is also an important term because what happens to one part of the system affects the other parts. Remove the roots from a tree and it will die. Break some of the electrical connections in a computer and it will not function. A serious accident to one member of a family will affect the other members of the family, and so on.
• The attributes of components refers to their characteristics. This is a direct function of their interdependence. If the roots of a tree are dry, if the connections of a computer are broken, if a member of a family is injured, then the dryness, brokenness and injury are all attributes that are part of the system and that impact other components of the system.
• When we speak of a system forming a whole, we are making a very significant statement about the order of the system. This wholeness has several important aspects. One is that the system functions as a whole and can be recognized as a whole. A family, a tree, a computer can each be recognized as a whole made up of parts. Another aspect is that removing one or more components undermines or destroys the wholeness. A branch is not a whole tree, a keyboard is not a whole computer, a mother is not a whole family. This aspect of wholeness is one of the most profound dimensions of reality. We may take it for granted, but it seems almost mystical or magical at times. The way a tree grows from a seed, or in some cases can be propagated from rooted cuttings, involves complex living processes that scientists still do not fully understand. The bonds between members of a family, though not physically visible, are so strong that they can motivate sacrifices even of life itself. The loosening of those bonds, when a child grows up and leaves home or when a divorce occurs, can be very painful experiences. The forces that make a system whole tend to keep it whole and to resist the break-up of the system. (Perhaps this cannot be said of an inanimate object such as a computer, but it is very true of living systems.)

2. The environment of a system consists of all objects and forces external to the system, such that a change in the environment's attributes or actions affects the system and vice versa. A pond is an environment for a fish. A home is an environment for a family. Von Bertalanffy and other systems thinkers define environment as external things which have a relationship with or impact on the system. Thus the environment for each system can change over time.

If you are a member of an American company, much of what goes on in Japan is not part of your environment. But when a Japanese competitor starts taking your customers' business, your environment changes dramatically. In fact many of the forces which are tending to shrink our world into a closely linked, interactive economy are forcing more and more people to think of the whole earth as their environment. From another perspective, the world economy is becoming a system in itself, and when we discuss subjects such as international weather and protection of the environment, the earth itself is viewed as a system of interactive parts. We may summarize all this by saying that "environment" is sometimes arbitrary and always relative to how we define the system we are focusing on.

3. All living systems are open systems. Open systems maintain themselves in a continuous interchange with their environments, importing and exporting matter and energy. One essential aspect of life is that every living organism depends on importing energy from its environment in order to survive. Some of that energy may be warmth from the sun or fire. Some of it is always in the form of food or nutrients, which the organism processes to release chemical energy or form new chemicals essential to life. And all living systems give off by-products, ranging from animal wastes to oxygen released by plants. The by-products almost always have lower-order energy than the ingested nutrients for that organism, although other organisms may still take energy from the wastes or inhale the oxygen from plants.

A closed system, such as a computer, can exist and persist without importing energy. But even then, any system in which there is physical, electrical or other motion must have energy from the outside at some point to power its motion, such as electricity which runs the computer. Actually a closed system is in many ways a product of the imagination of scientists who need to isolate experiments from their environments in order to observe the results, such as heating an enclosed gas to observe the increase in pressure. A closed system is an unnatural device, of little value to anyone except to observe how it functions in an experiment.

4. Open systems are always acting and changing. However, they have a strong tendency to reach and maintain a balance known as a steady state, or homeostasis. For example, human beings are always acting and changing, yet our bodies have a strong tendency to maintain a balance. When we use up our energy reserves, we become hungry. When we get overheated, we perspire. When we become tired, we desire rest. The steady state often represents an optimum condition that the system seeks to return to again and again, even though the system is in almost constant motion or change.

5. In open systems, the same steady state may be reached from different initial conditions and pathways. This is called equifinality. For example, if a person is hungry, he can eat all sorts of foods in all sorts of locations in order to restore his steady state. Equifinality is another way of saying that open systems are adaptable; if there were not different pathways to the steady state, the survival of the open system would be very much at risk.

6. Living systems tend to evolve toward higher levels of order in terms of differentiation and organization. This is one of the most profound aspects of living systems and represents the exact opposite of the entropy principle, which is a tendency to evolve toward greater disorder and uniformity. In living systems, there is what seems to be an innate drive for order. This higher order is achieved through processing energy. Whether the energy comes from sunlight or food, energy is essential for living systems, which have a natural drive for order. This includes human beings, of course. This principle is very important to understand and again demonstrates the profound significance of the relationship between order and energy in all living things.

7. In human systems, the primary means of evolving toward higher levels of order, differentiation and organization is the communication of information, especially in the form of decisions. Get a group of people together for the first time and they may just mingle around in a state of very low order. But once the group begins making decisions as to what it will do collectively, or how labor will be divided, it begins evolving toward a higher level of order.

8. Higher levels of order are achieved through the dynamic interaction of the components and through feedback. Through feedback, the effects of actions are transmitted back to the source of the actions to allow self-regulation. A thermostat is a classic example of a feedback loop in a system - when the temperature drops to a certain level, the thermostat sends a signal to the heater to send more heat. Feedback is essential to the success of any living system. For example, feedback from customers and the environment is essential to keep an organization functioning at peak performance.

9. A high level of order tends to make a living system and its parts function more efficiently, but it also tends to restrict or abolish the equality of power among the parts. For example, in most organizations a high level of order means different people have different power. There are typically a chairman, president, vice presidents, assistant vice presidents, managers, etc., each with a particular level of power. Even with teams, certain actions require a leader, even if that person's leadership is limited to a task or function.

10. Adaptive systems try different means to ends or goals and eventually settle into a pattern of interaction which minimizes conflict with critical factors in the environment. The tendency of many nations to join together through the United Nations to support world peace is a good example. An adaptive organization will explore different ways to adapt to changing customer needs, the competition, and market conditions.