Whatever the definition of complexity we should distinguish between the attitude of those that try to understand a complex system from those that have to act to modify it. The major preoccupation of the observer of a system is to avoid to perturb the system with the observation activity, while the reverse is the purpose of who has to decide what to do to change the system to move it to a specified goal.
Nevertheless the cognitive approach has been strongly influenced by the practical one. On one hand, the push to search for a "compressed algorithm" that can describe the system behaviour means to be able to use the algorithm not only to reconstruct actually observed behaviours but also to forecast the future ones. On the other hand, the decision-maker cannot act on the system unless he thinks he can predict the behaviour of the changed system. For him the availability of a compressed algorithm to describe system behaviour will certainly be very useful. Actually, one could advance a definition of a decision-maker as someone who has a kind of "compressed algorithm" to guide his actions to modify the system.
What happen, however, of this concurrent interest when the cognitive investigators have to recognise the irreducible aspects of parts-globality interactions in the system? The cognitive motivation of the historian and philosopher can be satisfied by the recognition of an unbreakable holism, of the impossibility to generalise the singularity of the events. But this recognition will be of no help to the decision-makers which will need nevertheless some practical guidance to the decision. This might explain a closer alliance between the decision-makers and the reductionist scientists (separation of the "two cultures").
Such alliance enter into crisis when the scientist himself has to recognise that there are conditions where the reductionist approach is not valid. There are islands of stability in "physical systems" where a compressed description can be developed. However, there are transition zones from one to the other islands for which the compressed description is no more possible.
The recognition of the impossibility to predict the future state of the system when passing through a transition zone might satisfy the cognitive motivation also of the physical scientist, and can lay a bridge between the "two cultures" toward a "nouvelle alliance". Our basic concern here is to understand to which extent such alliance on the cognitive front will be of any help to the praxis goal to intervene on a system to force it to follow a certain trajectory.
In fact, the reductionist approach is the only one available to act on a system. One need to breakdown it into parts small enough to be possible to intervene on them. One cannot act "directly" on the globality of the system to modify it! No matter how complex is the part on which we act it will always be "part" of a larger global system. In case the system is within an island of stability, the "compressed" description of the system will be of help to the decision maker to predict the future state of the global system after having modified one or more of its parts, essentially because the system will see the modification as a "small perturbation" that does not change its basic structure (it has "slacks" available to accommodate the changes). When however the decision-maker act on a system which is in a transition mood, no perturbation can be considered small enough not to influence the system globality. Will it be possible to predict the influence of the perturbation on its future trajectory? Paradoxically, the situation is, in such condition, more favourable to the practical approach than to the cognitive one. In fact, the basic difficulty for the cognitor is actually the high sensitivity of the system so it might be impossible not to perturb it while observing. The practitioner instead aims at modifying the system, so he can take advantage of the system sensitivity to "move" it with very small actions. And because of the intervention, the system will "choose" between different potential trajectories. The problem for the decision-makers is whether or not he has tools to forecast the system behaviour, to see the potential alternative trajectories and whether or not the system is on a "saddle point". In this latter condition he could hope that a small intervention might be enough to "break the symmetry" between the alternative routes. Of course, the decision-maker might feel the transition, but not be (himself and the subsystem on which he can directly act) on the "verge of the saddle". This might explain why there are successes and failures in the attempts of different actors to react to the same challenge.
Could
here the "nouvelle alliance" between humanists and scientists help the
decision-maker? Is there a "wisdom" (knowledge and virtue) of
complexity available to guide the activity aimed at changing the system (problem
solving)? The word "wisdom" is used here as a counterpart to
rationality. The "rational" behaviour of decision-maker underline
optimisation (minimum use of resources to produce the sought effect) which might
be possible only when a compressed description of the system is available. A
"wise" approach should assure that at least qualitatively (good enough
solution) the objective is met (the change is in the desired direction), even
when not in such condition.
The situation that ask for a "wise" approach is quite common. However we tend not to recognise the difference with the cases where optimisation is possible thanks to the availability of practical recipes for actions (that condense the wisdom coming from past knowledge on decision-making for problem solving). The problem utters to our attention all the times we think we are confronted with a completely new situation, when we feel a transition to an unknown territory. A recent important challenge to decision-makers comes from the feeling that a "globalization process" is underway which is transforming our social, economic and technical systems.
We will use the case of the "globalization challenge"
that face the decision-makers to develop a positive response to the above
question: whether or not we can develop a praxis to deal successfully with
complexity.