Boundries define systems and sub-systems. The boundry is the interface between what is part of the system and what is part of the environment. Events that occur at the boundry are significant in defining the nature of the system. One could say that since everything is part of one greater system, what is the point of looking at sub-systems? I contend that it is critical to consider sub-systems because the manner in which system components (individual, organizations, etc.) view themselves influences how they make decisions. Decisions are "always" made to maximize the benefit accrued to the system. If I see myself as the system and everything and everyone else as part of the outside environment, I will make decisions that maximize my benefit only, without concern for the outside environment.
If I see my family as the systemand everything and everyone else as part of the outside environment, ...
If I see my organization as the system...
If I see my country as the system...
If I see the world as the system...
Of course most people do not consciously go through the process of thinking about systems, but if you look at their decisions, it is a proxy for how they see their world. If you logically look at this you might ask why wouldn't everyone want to maxmize the benefit for the most people? The answer is in timing: the smaller the system, the faster the feedback loop, thus the quicker the gratification. Unfortunately the quick gratification does not always lead the the best long term ooutcome.
Now as systems practitioners, how do we get people to look past short term gratification and embrace the longer term benefit? The answer is increased human interaction. Build the network. By increasing the connection between people we come to better empathize with their situation and make their needs our own. We internalize externalities. In doing this we see ourselves as part of the larger system and are therefore willing to wait for the greater benefit that accrues to the larger system. The simplest way to do this is through dialogue, simple conversation. Our jobs as practitioners is to facilitate the conversation. The rest will emerge.