An element is a building block of a system that can be also considered separately, with its own properties, features. A system may be viewed as a whole or as a combination of elements. Elements need to be properly identified to describe a system 35, however listing elements is not enough to present a system. How elements interact is crucial.
We can focus on a system as a whole and study the behaviour of elements in their interconnectivity within the system. This approach is called holism . Here it is the behaviour of the whole that is important and it is this behaviour that is studied. The behaviour of individual elements is of less interest and is viewed only as part of the overall system behaviour. On the contrary, reductionism is the theory that assumes that we can understand system behaviour by studying the elements and their interaction.
These two approaches parallel analysis and synthesis. In the reductionist approach one can reduce the study of a complex system to analysis of smaller and presumably simpler components. While there are more components to consider, their complexity will be lower and they will be easier to experiment with and to analyse. However, this analysis may not be sufficient for understanding the whole system behaviour because of the emergent features that appear only at the whole system level. The holistic approach is essential to understand the full system operation. However if the behaviour of the elements is already well studied and understood it is easier to understand the whole system performance.
If you cut a cake into pieces you would not call these pieces elements of a cake, because they have no particular features to distinguish them from one another in the cake—there may be any number of pieces, and as parts of a cake they are all the same. Besides, the pieces do not interact and do not offer any other properties except those delivered by the cake as a whole. The only difference is in size. Just a piece of a whole is not an element. If you divide the cake differently, separating the crust, the filling and the topping, then you will get something quite different from the whole cake. It will make much more sense to call these parts elements of the whole. The taste and other properties of each of these elements may be quite different: the taste of the crust is not the same as the taste of the filling and not the same as the taste of the cake as a whole. Now there are ways to distinguish one element from another. The new taste or look that are created when these elements interact, are the important feature of the system.
Parts simply brought together do not necessarily make a system. Imagine ten people in a big room. They may be elements of a system in terms of being separable and looking differently and carrying some unique properties. However, just as a group they would hardly be called a system. However adding some rules of interaction, we can start a basketball game when the group of people becomes a system that exhibits some new additional properties. It is these properties that can draw thousands of people to watch the game. We get some additional emergent properties from the whole, which none of the elements possess.
The population of Enschede in a holistic approach would be described by some general variables, like numbers, birth rate, mortality, education level. We may include more details also measuring religious preferences, consumption patterns, affluence, etc. But still we will be describing the population as a whole. Alternatively, we could present this same population as a collection of much smaller entities, say, age groups, or urban clusters, or even individuals, and then describe each of these entities separately. The properties of the Enschede population as a whole will then emerge from the joint performance of these separate entities.