Modern study of emergence tends to separate "emergence" into two broad categories: weak emergence and strong emergence. This distinction is made by Mark Bedau, among other commentators. The differences between the two species of emergence are significant.
Strong emergence: This is the species of emergent discussed in the first post in this series--an emergence that is ontologically separate from its microstructure, not derivable from that microstructure, and capable of exerting downward causation on the functioning of that microstructure.
Weak emergence: Weak emergence is the set of phenomena that is theoretically reducible to the known laws governing the microstructure, but where the calculations required to predict the resulting phenomena are so complex as to be effectively impossible. Instead, with weak emergence, these calculations are carried out by means of simulation.
This study of weak emergence, also called more broadly the study of complexity, is seen in the (overlapping) modern disciplines of systems theory, neural networks theory, dynamical systems theory, agent based modeling, complex adaptive systems, etc. One of my favorite authors, John Holland ("Hidden Order" and "Emergence") discusses this form of emergence.
The study of strong emergence has been less fruitful, so far, in science, perhaps because like weak emergence, it is not practicably reducible, but unlike weak emergence, it is also (so far) not capable of simulation. Strong emergence--as is pointed out by many of its critics--is primarily either a subject of philosophical discourse or it is narrowly useful as a theory of human consciousness that really hasn't changed much since Roger Sperry's groundbreaking theory of consciousness in 1969.
For this blog, and the theory of Rhizome, are we interested in the effects of weak or strong emergence? In my mind, the answer is clearly "both." There is little doubt that human systems, evolving civilization, group dynamics, and economic dynamics exhibit weakly emergent traits. The study of weak emergence, therefore, will likely give us insight into the operation of these systems, how to shape them, and the viability of alternative structures. My theory of Rhizome communication, for example, and its information processing and economic coordination capability, can be compared to the capabilities of more hierarchal structures by way of simulation. The functioning of these various structures are fundamentally reducible to known and understood interaction of their microstructure, but the resulting calculations are simply not feasible, and therefore the study of weak emergence may offer useful insights into their functioning. I am also, however, interested in the potential strong emergence in human civilization. Even if strong emergence exists nowhere but human consciousness, that alone is interesting enough to warrant further exploration--at a minimum, there is the question of whether a "weakly emergent" phenomena like human civilization and economics can be meaningfully separated from the strongly emergent consciousness present at each individual human component in the microstructure...
Intuitively, however, I think there is a good chance that strong emergence plays a much more significant role beyond human consciousness--in group dynamics, communication, cultural trends, and economic coordination. This is where I think emergence has something fundamentally new and valuable to teach us--beyond what we can learn from studying complex human systems through the lens of weak emergence. What exactly this influence of strong emergence is I do not know--one reason I find this so fascinating is that it is a possibility that is simply not being studied or considered. The possibilities seem endless. I do, however, have a theory, specifically pertaining to the influence of strong emergence on coordination and information processing.
My theory is that, just like human consciousness (which I presume to be strongly emergent) offers superior coordination and information processing capabilities when compared to non-strongly emergent coordination and information processing (such as computers), I think that strongly emergent phenomena in economic coordination, dynamic network structuring, and human communication may dramatically increase the efficiency of operation of human systems that foster strong emergence. Such strong emergence may be present to varying degrees in our current economic and political systems, but my hunch is that structures designed to better foster strong emergence would leverage these effects to a much greater degree. Specifically, as I hinted at in the first post in this series, decentralized but well connected networks (e.g. Rhizome) that mimic the connectivity of the human brain may, like the human brain, foster strong emergence. Hierarchy, on the other hand, may actually act to dampen strong emergence--in fact, one of the main evolutionary features of hierarchy in human civilization may be that, by dampening strong emergence, system control is maintained at the top of the hierarchy, rather than ceded to some degree to a strongly emergent and ontologically distinct phenomenon. These ideas are, of course, still very fuzzy, difficult to articulate, and poorly supported, but the potential here makes them worthy of further investigation in my opinion.
While strong emergence may not be subject to study by simulation, as weak emergence is, I think it may be replicable. That is, if we accept that strong emergence is derivative of an underlying microstructure, then by replicating that microstructure, or at least the salient features of that microstructure, it may be possible to foster strongly emergent phenomena. This has always been an influence in the theory of Rhizome--largely unstated until now because I haven't had the tools to explain why this was anything more than intuition and speculation on my part. While I think Rhizome, as a theory, is valid even if there is nothing more than weak emergence in this world, the potential to leverage strong emergence may make the theory even more robust.
Readers may also find my litigation checklist of interest.