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?