Systems philosophy is the study of the development of systems, with an emphasis on design and root cause analysis. Systems philosophy is a form of systems thinking.
Ludwig von Bertalanffy, the founder of systems science, categorized three domains of systemics: the philosophy of systems, the theory of systems, and the technology of systems. This was later modified by Béla H. Bánáthy of the Primer Group to a fourfold model, the philosophy, the science, the methodology and the application of systemics. The philosophy and the science of systems constitute the knowledge of systems; the methodology and the application constitute the action of systems.
According to systems philosophy, there are no "systems" in nature. The universe, the world and nature have no ability to describe themselves. That which is, is. With respect to nature, conceptual systems are merely models that humans create in an attempt to understand the environment in which they live. The system model is used because it more accurately describes the observations.
Because systems are models created only for understanding, the most fundamental property of any system is that a system has an arbitrary boundary. Humans create the boundaries to suit their own purposes of analysis, discussion and understanding. This is true of every conceptual model that was devised through which humans try to understand the universe.
Arbitrary does not mean random or meaningless. Arbitrary merely means without previous dependency. We assume that the Universe is objective, but our experience is tempered by our subjective understanding. We see what we look at.
Systems are further expressed by listing the elements relationships, wholes, and rules associated with that system. Again, this is an arbitrary exercise true of all models humans create.
What are system elements? Elements might be tangible or intangible, real or imaginary. Conceptually, elements are merely terms and definitions. For example, in the system or model of measurement, the arbitrary terms of height, width, and length describe the three dimensions of physical space. Additional elements of that system describe those three fundamental elements: inches, feet, meters, kilometers, etc. However, those elements are meaningless without definitions. Definitions are necessary for all terms, whether or not those terms represent tangible or intangible elements. Definitions and terms are added as necessary to help understand any model.
Relationships are ontologically different from elements, just as the meaning of these words differ from the letters making it up, an element is a thing, a relationship is what a thing is doing. The relationship constrains the system into having at least two elements. Often the relationship has an emergent property, and in most cases these elements and relationships emerge as a whole.
A systemic whole is directly related to the relationships of elements, in that our experience of such a relationship is as a whole. One of the significant characteristics of a system of this type is that there are properties of the whole that cannot be found in the elements. Meaning, for example, is not found in the properties of these letters you are reading.
A rule is anything describing how the elements are related or behave dynamically. Rules describe how a system functions. Rules describe how system elements interact, and those original arbitrary boundaries establish finite limits of how the rules affect the elements. Inches and feet, or meters and kilometers, are elements of the system of measurement, but the relationship of those elements are rules. There are twelve inches in a foot, 1,000 meters in a kilometer, etc.
A system with no elements and no rules—boundaries only—is called a null system.
Change any boundary, element, or rule in any system and a completely new system appears. Observations made in one system might, or might not, hold true for a different system.