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Greater Than the Sum - Part-Whole Relationships

Systems are by their very nature collections of multiple things, so it's not surprising that one of the most fundamental distinctions in systems theory is that of "part" and "whole." What do we mean by "part" and "whole" in a systems context? A part can be almost anything. For instance, it might be a piece in a machine - a wheel is a part of the larger whole that we call an automobile. Or it might be an organ in an organism - a heart is a part of a body. In most systems part-whole relationships exist in nested hierarchies. For instance, a hubcap is a part of the whole wheel which is in turn a part of the automobile which might in turn be considered part of a fleet of vehicles. Or, a cell is a part of the heart which is part of the body which is in turn part of a class or group of organisms. But the part-whole distinction is more than just a physical one. We can also talk about part-whole hierarchies in concepts. For instance, our idea of the concept of humanity consists of parts like nationalities and sub-parts like people from different states or towns. Or, we might divide the whole concept of humanity into the parts of those who were born in different years, subgroups who are male and female, and subgroups of those who have brown hair or are right-handed. As these examples show, the part-whole concept is a universal one that can be applied to virtually anything.

When thinking of parts and wholes it is also important to keep in mind that in addition to the whole and the parts that it is made up of, we also can think about the relationships between these as something that is distinguishable and meaningful (almost as if the relationships are separate "parts" of the part-whole distinction!) For instance, in a car there is the whole of the car, its various parts (e.g., wheels, engine) and the relationships between these. This idea of the importance of relationships is central to systems thinking. It gives rise to the famous saying that "the whole is greater than the sum of its parts" that you have probably heard of. We have to be careful about this saying, however. In mechanical systems, the whole is very often precisely the sum of its parts. You can take a car apart and reassemble it and it will work. However, in dynamic or living systems this is not the case - you cannot take a human body apart and then reassemble it and expect to have a working system. So, the phrase "the whole is greater than the sum" really is meant to refer to dynamic systems, not mechanical ones.

Part-whole relationships are everywhere in evaluation and it is critically important that we use these concepts in our evaluation work. For instance, an organization (whole) will often operate in multiple program areas (e.g., an educational or outreach organization might have programs for children, teens, adults and the elderly; or programs in health, education, environment, science, etc.); each program area (whole) might have multiple programs (parts); each program (whole) will usually consist of multiple activities (parts); each activity (whole) can typically be broken down into different tasks (parts); and so on. Or we can view different levels of part-whole hierarchies in terms of stakeholder groups. In an educational or outreach program we might think of stakeholders at the program level (participants, their families and program deliverers), the organizational level (program managers and organizational administrators), the local context (local officials or the local public), the funders level (e.g., state or national) and even the societal level (Congress or society as a whole). The idea of part-whole relationships is essential in the development and implementation of our programs. It is central to our description of the program, the development of logic or pathway models, and the analysis of stakeholders and their interests.