ABSTRACT
This chapter describes the description of kinds of layers and types of entities and their properties. Layers and entities have been discussed in other areas, especially in the philosophy of science and in epistemology. It begins by addressing the analogue situation in the study of cognitive systems to illustrate the reasons and the implications of the division into various levels of description. The chapter discusses the various entities, such as the individual, group, organisation or network, in greater detail. It deals with two particular aspects of the various entities—the system's perspective as such and the complexity and adaptation of entities. Although the different characteristics of the entities are important in relation to their behaviour and interaction in the specific areas and levels, the system's perspective focuses on entities in terms of complexity, adaptation, composition of parts, and boundaries between system and environment. Finally, it presents the first steps towards a systematic approach to sustainability.
