[Next] [Previous] [Top] [Contents]
What is Complexity? - The philosophy of complexity per se with application to some examples in evolution
The first question is about the scope of complexity. Since I am writing from a pragmatic perspective, I am only concerned with the useful application of this concept. If complexity could theoretically be applied to a particular system but would be completely impractical, this is of no help.
The most obvious use is with reference to real systems: "The brain is complex." or "Humans are more complex than amoeba.". This approach has several severe problems:
- The "true complexity" of real objects (if it existed) would probably be totally beyond us;
- The complexity of things seems to vary depending on which aspect you are concerned with;
- Any "real" complexity is irrelevant, as we never interact with the total systems, only certain aspects of them at any one time;
- The complexity of an object is only revealed though interaction with the complexity of another system (typically us);
- There would be little connection between this "real" complexity and the complexity of that object as represented in communications about it.
All of these problems are connected. We are ourselves systems that can deal with limited complexity (as are all the systems we have created). In fact, I would argue that, the reduction in complexity of our inter-action with any part of reality is an essential component of our existence (see Section 7.3).
In response to these problems many authors*1 have stressed that complexity only makes sense when considered as relative to a given observer. Thus there is an established split between the "system complexity" and the "observer complexity". The system complexity is the complexity of the system w.r.t. the observer and the observer complexity is the complexity of the observer w.r.t. the system. There are still some problems with this approach, namely:
- It is still difficult to ascribe useful meaning to the complexity of the observer w.r.t. the system unless the system is an observer too, otherwise the observer is itself unobserved and so undefined in the sense of the "real" systems above;
- The complexity of the system w.r.t. the observer will still vary according to which aspect of the observed system is being considered by that observer;
- If the system as observed is not representable in terms of a communicable language (i.e. it is restricted to an internal model of some kind) then this model suffers from many of the above difficulties w.r.t. ascribing complexity to real objects.
For these reasons I, like others*2, am going to restrict my application of the concept of complexity to representations within finitely presented languages. Thus talking about complexity will necessitate indicating the language of representation that this is relative to. This will help to clarify some of the confusions around this concept and make the study of the evolution of complexity more productive.
What is Complexity? - The philosophy of complexity per se with application to some examples in evolution - 14 JUN 95
[Next] [Previous] [Top] [Contents]
Generated with CERN WebMaker