Friday, July 21, 2006

What is a Complex Adaptive System?

The Simply Complex Law
By J.B. Ruhl
Post 2: What is a Complex Adaptive System?
July 21, 2006

Complexity theory is the foundation for the study of complex adaptive systems (CAS). A CAS is a heterogeneous collection of interacting agents that evolves over time at the macroscopic system scale. Any agent in the system interacts with one or more other agents in any “move” of the system according to rules. Some or all of the agents in the system also base their decisions about what to do in the next move based on the macroscopic state (macrostate) of the system or on conditions exogenous to the system having some impact on it.

So far, pretty straightforward. It gets interesting, however, as we tinker with the number of agents, their heterogeneity, the number and tightness of couplings between them, and the rules of each move. The upshot is that, although all the agents are basing moves according to strict rules of interaction and response, it can become impossible to predict the evolutionary path of the system very far into the future. Complexity theory describes a number of attributes that account for this property of CAS behavior, which I will cover in the next two posts. For deep background reading on this topic, the classics are At Home in the Universe by Stuart Kauffman, and Hidden Order by John Holland.

Next: What attributes of a complex adaptive system make it complex and unpredictable?

4 Comments:

Anonymous Bruce Boyden said...

I'm really looking forward to the next post in this series. I've been thinking about the application of complexity theory to law ever since reading Mitchell Waldrop's "Complexity" in the early 90s, and then Holland, Kauffman, etc. But one issue I've always had is, while it may be interesting to think about legal systems as complex adaptive systems, do any tangible results follow from that? Or is it just an interesting metaphor?

7/21/2006 4:08 PM  
Blogger J.B. Ruhl said...

I'm certainly going to try to convince you (and all readers) that there are tangible results to follow. But it will take several posts over the course of the next week or two to lay out my argument for why. JBR

7/21/2006 4:39 PM  
Anonymous Paul Gowder said...

Question: to the extent the claim is that the law is a complex system, to what extent does it matter for this classification if the actions of a few agents are dominant?

For example, in the U.S., Congress, the Supreme Court, and the President can, if they so choose, utterly swamp the effects of all other actors. By this I mean that regardless of, say, the interacting effects of millions of litigants and thousands of judges in developing a body of law, Congress can turn all those effects to noise with a single legislative act. Does that make the law a non-complex system?

7/21/2006 5:47 PM  
Blogger J.B. Ruhl said...

Not at all. For one thing, what makes our legal system so dynamic is that it is hard for any actor (or CAS in the nested hierarchies of CASs) to do what this comment hypothesizes. In any event, assuming Congress could do this and did so on a very important question for many other actors, the question is what would happen next. I'm confident there would be a wave of responses thoughout the legal system--challenges in courts, action at the state and local levels, etc., and I doubt anyone could predict the unfolding of events very far into the future. In short, one can't identify a discrete event, or the possibility of a discrete event, to evaluate whether a system is complex or not.

That said, of course it does matter how the system is configured in terms of long term resilience and fitness, terms I will introduce in the next post. And it certainly can matter in this respect whether some component of the system is dominant and impervious to input. There is, in other words, a difference between a democracy and a dictatorship, but it's not that one is a complex system and the other is not. It's about relative fitness.

I'm hopeful questions like these continue, and that I will answer them satisfactorily over the next few weeks as I lay out the general theory. JBR

7/23/2006 3:57 PM  

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