 An integrative level is a pattern of organization emerging on pre-existing phenomena of a lower level. Typical examples of this include life emerging out of non-living substances, or consciousness emerging out of the nervous system, or social institutions emerging out of individuals interacting. As component parts combine to produce larger functional holes in a hierarchical series, one cannot explain all of the properties at one level from an understanding of the components at the level below. This idea of integrative levels is central to the theory of emergence, as integrative levels can be understood as the product of the process of emergence, having played out to generate two or more qualitatively different levels of organization. The concept of integrative levels of organization is a general description of the evolution of entities through successive and higher orders of complexity and integration. This process may be seen as discontinuous as it passes through a series of different levels of organization, physical, chemical and sociological, but it may also be seen as continuous as similar dynamics within the process of emergence takes place on the different levels. In this continuous evolution of entities, new levels of complexity and organization are superimposed on the individual units by the combination and integration of those units into single higher level systems. What were holes on one level become parts on a higher level. Each level of organization possesses unique properties of structure and behavior. Knowledge of the laws of the lower level is necessary for a full understanding of the higher level, yet the unique properties of phenomena at the higher level cannot be predicted a priori from the laws of the lower level. The laws describing the unique properties of each level are qualitatively distinct and their discovery requires methods of research and analysis appropriate to that particular level and type of organization. Quite different tools are needed for understanding the different levels. We cannot use a microscope to study an ecosystem or a whole city. The theory of integrative levels engenders a number of principles governing the makeup of these hierarchical organizations. Firstly, the higher levels depend on the lower levels which would seem quite apparent. Higher level phenomena emerge from the more basic constituents and without those constituent parts any form of emergence becomes impossible. This would imply that the higher levels in the hierarchy are inherently more precarious due to this dependency on the lower levels. Secondly, the higher up the level the fewer the instances. This again would appear self-evident as emergence involves a process of synthesis which is the merging of different things and thus on every higher level the number of elements will be reduced because they're being combined. Thirdly, the sequence of levels is often described as one of increasing complexity. This is far less self-evident and a somewhat debatable proposition as it depends on one's definition of complexity for which there are a number of different interpretations. One interpretation of complexity that would be congruent with this proposition is the idea that complexity is a combination of both integration and differentiation as we talked about in a previous module which describes a system that has many diverse parts which in turn are also interconnected and interdependent. This is one interpretation of a complex system that is congruent with this hypothesis because through the process of synthesis systems are conceived that have increasingly many parts which are also increasingly interdependent and thus increasing their complexity as we go up the levels in the hierarchy. Hierarchy and emergence give rise to the design principle of encapsulation which describes how smaller subsystems are nested or encapsulated within larger structures. Key to this design pattern is the use of abstraction meaning the successive removal of detail as smaller locally specific sub-components are nested within larger, more generic processes and structures. Hierarchical encapsulation through abstraction is central to the structural design of complex systems of all kind and can be seen as a fundamental pattern of functioning ordered systems of complexity as it works to distribute components out across the different levels. For example, human cognition in the brain is structured through this form of hierarchical abstraction. In the different levels of cognition more basic neural networks are formed and then grouped to create the input for higher patterns. The lowest levels of abstraction are connected to the senses directly providing the data or facts that are inputted to the system. We then build up higher level patterns through a process of synthesis abstracting away the concrete details in synthesizing them into generic concepts. In this way we get a hierarchy of levels with different organizational structures emerging on the different levels. This nested hierarchical structure is seen within fractal forms that exhibit self-similarity across various scales of magnitude. Examples include everything from the structure to the capillary network in animals to river networks and the structure of mountain ranges. This self-similarity or fractality implies a particular kind of structural composition or dynamic behavior wherein the fundamental features of the system exhibit an invariant hierarchical organization that holds over a wide range of spatial scales and can be derived from simple iterative rules. The process of emergence creates new levels of organization, new structures that have some integrity to their parts or within which some new process takes place thus creating their own distinct patterns. This new level then feeds back to shape and constrain the components on the local level. We get the emergence of some process but for that process to take place there needs to be an enabling structure. That structure then defines some order to the system and the components must differentiate their state to perform the various structural and functional roles required to process the resource on the macro level as we've previously talked about. This need for the high levels to constrain and control the lower levels in order to enable higher level processes then creates a complex dynamic between the micro and macro levels as they become interdependent on each other. This is most evident from the way the human body as a whole regulates every local component of itself to enable global processes such as respiration and digestion to take place effectively. This is a micro to macro to micro feedback loop through the many different emergent levels from the cells to the tissues to organs and all the way up to the entire organism.