The observer sets the boundaries of the purposive system and decides which role should be attributed to which system component. On the one hand, the basis for choice is the observer's own purpose. On the other hand, if changes in one role are contemplated, then the impact of or constraints on those changes on the other roles must be considered. A researcher in forest eco-systems may have to worry about the removal of a tree, if it is available for logging, or not, if it is a popular tourist attraction. In creating a toolset with which to understand complex systems, one of the most important things to consider is the rules by which we will apply the various tools.
Singerian systems are thus pragmatic and conditional.
They assume that the truth content of a system is relative to the objectives of the inquiry. So we see that systems philosophies support a recursive approach to the world. Our method of inquiry into the system can take whatever form it needs to, based on the problem to be solved, as long as it is kept to a firm philosophic basis. Our vertical view of the system can start wherever it needs to, also based on the problem to be solved, as long as it covers an appropriate number of systemic levels. And our horizontal view of the system may employ any perceptual filters necessary to help us gain understanding, solve the problem, or better manage the relationships.