Emergence

Emergence is...

1) ...what parts of a system do together that they would not do by themselves: collective behavior.

2) ...what a system does by virtue of its relationship to its environment that it would not do by itself: e.g. its function.

3) ...the act or process of becoming an emergent system.

According to (1) emergence refers to understanding how collective properties arise from the properties of parts. More generally, it refers to how behavior at a larger scale of the system arises from the detailed structure, behavior and relationships on a finer scale. In the extreme, it is about how macroscopic behavior arises from microscopic behavior.

According to this view, when we think about emergence we are, in our mind's eye, moving between different vantage points. We see the trees and the forest at the same time. We see the way the trees and the forest are related to each other. To see in both these views we have to be able to see details, but also ignore details. The trick is to know which of the many details we see in the trees are important to know when we see the forest.

In conventional views the observer considers either the trees or the forest. Those who consider the trees consider the details to be essential and do not see the patterns that arise when considering trees in the context of the forest. Those who consider the forest do not see the details. When one can shift back and forth between seeing the trees and the forest one also sees which aspects of the trees are relevant to the description of the forest. Understanding this relationship in general is the study of emergence.

Acording to (2) emergence refers to all the properties that we assign to a system that are really properties of the relationship between a system and its environment.

A useful example is a key. A key has a particular structure. Describing its structure is not enough to tell somone that it can open a door. We have to know both the structure of the key, and of the lock. Without describing the structure of either, however, we can tell someone that it can unlock the door.

One of the problems in thinking about the concepts of complex systems is that we often assign properties to a system that are actually properties of a relationship between the system and its environment. Why do we do this? Because it makes thinking about what is going on simpler. Why can we do this? Because when the environment does not change, then we only need to describe the system and not the environment in order to give the relationship. Thus, the relationship is often implicit in what we think and what we say.

The second aspect of emergence (2) is related to the first aspect (1) because the system can be viewed along with parts of its environment as together forming a larger system. The collective behaviors due to the relationships of the larger system's parts reflect the relationships of the original system and its environment.

The role of relationship:

Both (1) and (2) have to do with relationships, the relationships of the parts, or the relationship of the system to its environment. When parts of a system are related to each other we talk about them as a network, when a system is related to parts of a larger system we talk about its ecosystem.

The role of pattern:

When there are relationships that exist between parts of a system we talk about the existence of patterns of behavior.

The idea of emergence is often contrasted with a reductionist perspective. The reductionist perspective thinks about parts in isolation. It is the often vilified "anti-complex systems" view of the world. However, even the idea of a system is based upon a partial reductionism. To understand this, one should carefully understand the notion of approximation or "partial-truth" which is essential for the study of complex systems.

 

Copyright © 2000-2003 Yaneer Bar-Yam All rights reserved.