Wednesday, July 26, 2006

What Is Fitness?

The Simply Complex Law
By J.B. Ruhl
Post 6: What Is Fitness?
July 26, 2006

Several comments to previous posts have rightly suggested that I should have included a definition of “fitness” in my description of complex adaptive system (CAS) properties. As the discussion has turned to law as a CAS, I’ll offer both a general and a law-oriented discussion of fitness in this post.

Most people are familiar with the description of fitness from evolutionary biology as the measure of survival and reproductive success of an organism, or a type of organism. But we need a more general definition for purposes of complex systems theory, because some systems don’t “reproduce” in the biological sense. So, what are we measuring in the case of CASs generally?

The underlying theme of the concept of a system’s fitness is that we are interested in what happens to the system over time in a changing environment. A CAS employs a schema for dealing with what the environment throws at it, for staying resilient over time. The schema consists of a model of the real world and a search algorithm for discovering rules for successfully surviving in the changing environment. In Hidden Order, John Holland suggests that fitness in the generalized sense thus must have to do with the “strength” of the schema.

Of course, the schema may (and strong ones likely will) involve testing different configurations and distributions of system characteristics, and devising new search rules, and thus the system at any one moment may not look like the system in previous or later states, and there is no steady end state in which indefinite survival is assured regardless of environmental change. So, there has to be some room for change bundled into the measure of fitness, but we also need to differentiate between change of that sort and change that is the direct result of perturbation and which may move the system through a critical threshold after which it really isn’t the same system as before. So it becomes pretty complicated when we ask about the fitness of, say, an ecosystem. It requires that we agree on what it is about Ecosystem X that makes us identify it as Ecosystem X, and from there that we can accurately measure those attributes.

Fitness in the legal system presents that kind of complicated, multi-attribute inquiry. Lawyers seem to be comfortable describing boundaries for different legal systems, such as the common law, administrative law, environmental law, and so on. So I think when we ask about the fitness of any such legal system, we want to explore its model of the real world, its schema for dealing with change in the real world, and how successful it is in that respect over time. By success I mean retaining its basic institutional design—e.g., what it is about the common law system that causes us to describe it as the common law system. In other words, I don’t propose using normative measures for defining fitness, such as some measure of just results, efficiency, or legitimacy. The normative perceptions other agents and social CASs have of a legal system have to do with the selection pressures they may put on the legal system in their co-evolutionary dance, but what we measure for inquiring about the fitness of a legal system is how well it’s schema has allowed it to maintain its institutional design over time.

Next: Is a Complex Adaptive System just a metaphor for the legal system?


Anonymous Anonymous said...

[I also posted this below]

I liked the post on fitness, though I only read it today, after I posted the earlier comment.

The post makes reference to survival, and of course for a legal system as for an organism, survival depends on reproduction over time. Is why biologists use reproduction and not survival of the individual organism as a measure of fitness.

Accordingly, I still think reproduction can be a useful measure of fitness with regard to particular laws and legal systems, so long as one doesn't get too general about what it is that is reproducing.

Reading the social norms literature across a wide variety of disciplines (not just the law and economics version), it is possible to think of the process of legal codification as a mechanism to transform a social norm into a legal rule, and thus ensure its reproduction over a longer period of time. A legal rule has a lot more staying power than a more informal norm or custom or rule. A community delegates responsibility for monitoring and enforcement of the rule (necessary to its reproduction) to the state.

The legal rule gets modified constantly--in operation, in geographic dispersal, via amendment, via interpretation, etc. (so reproduction with some recombination or mutation). Sometimes, the legal rule is thrown over by a competing legal rule, or extinguished by a change in the environment (so what would our abortion rules look like if the fetus technologically could survive from conception onwards outside the womb?).

Kauffman makes the point that you can measure fitness at different levels (for example, the ability to catalyze an enzyme), but the ultimate measure of fitness is still reproduction.

I think referring to the fitness of the common law system is still possible, so long as one recognizes that you must have a pretty good idea of what features characterize a common law system. I think it's more useful to focus on the fitness of those individual features (e.g., judicial interpretation of law that creates binding precedent).

7/27/2006 2:19 PM  
Blogger J.B. Ruhl said...

Anonymous and I appear to be getting closer to being on the same page! I appreciate the refinement in my details that his or her comments motivated.

I agree that in a nested hierarchy (or to use Holling's term, panarchy) of CASs, there are many scales at which to measure fitness. So there are particular doctrines in the common law, particular institutional features of the common law, and the common law.

I am not so sure a legal rule necessarily has more staying power than more informal customs or rules, depending on what one places in each category. Some societies rely primarily on custom, and have done so for quite a long time, and some social norms displace legal rules even in societies that rely heavily on legal rules.

If by reproduction in the legal CAS you mean somethig like "staying power," and by staying power you mean something like continued application of a rule, continued use of stare decisis in the common law, and continued use of the common law as an institution, we're good.

7/27/2006 3:08 PM  

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