Emergent phenomena are often defined in one of three ways:
1) if the behavior of a phenomena is not simply the sum of it's reducible parts
2) if the behavior of a phenomena is not predictable given full knowledge of it's parts
3) if the behavior of a phenomena exhibits novel causal efficacy not exhibited by it's parts
For those looking for more background on the topic, the philosopher Massimo Pigliucci presented a four part commentary on some important papers in the field at these 4 links: part 1, part 2, part 3, part 4
The discussion at the 'Moving Naturalism Forward ' conference that I will now summarize was introduced by Terrence Deacon and can be found here.
I found Deacons approach to the topic very compelling. I would recommend anyone interested in the topic to check out the first 2 to 25 minutes of the video where his approach is spelled out.
Deacon begins by addressing the question 'What fits in naturalism'? Deacon feels that Rosenberg's approach and that of most naturalists in general is overly eliminative. In particular Deacon would like find a place for teleology ('organisms have an end-directedness') in biology. While most in the room would consider Deacon to be an anti-reductionist he considers what he does to make full use of reduction. He feels however that meaning has causal efficacy in the world, and that we need to think in terms of 'processes and dynamical complexities' to begin to address how this may come to be.
Deacon does not feel that talk of bottom-up and top-down causality is useful. He feels that the organization of the structural dynamics is what really matters. 'The work' he states 'is mostly done by constraints' on structural relationships. The constraints determine 'what does happen, not just what could happen'. In Deacons view the causality in the world is not in the 'stuff', but in the 'organization'.
Don Ross suggests that Deacon talk scales rather than levels which Deacon is fine with. Steven Weinberg however, is adamant that the language of levels is retained. He as a particle physicist feels there is a 'fundamental level of truth which determines every thing at higher levels'. Ross is on board with getting away from the top-down, bottom-up trap in compositional terms. He would like to employ scales in relation to how universal a theory is. In this way he sees quantum field theory as universal. Using Deacons terminology quantum field theory would constrain other theories. I agree and my reading of this is that complementarity would be perhaps the general universal principal that applies to all scales of emergence. Deacon provides a slightly less general, but more explanatory model that incorporates a type of complementary interdependence.
Deacon is very interested in the origin of life and approaches emergence from that vantage point. The origin of life had to in his view be relatively simple, but yet it represents a dramatic 'phase change'. This is where the very beginnings of end-directness emerge. Deacon feels we can tell this story by looking at information, thermodynamics, and organization. Within these 3 areas he sees his conception of 'constraint' as a common thread.
Life has to generate regularity, and also has keep that regularity from dissipation. To do this it has to constrain the thermodynamic tendency towards dissipation. The organization must be limited in certain ways. Deacon then describes a molecular model in which interdependent self organizing systems generate constraints (boundary conditions) on each other. The constraints can then be remembered as information and passed on.
Deacon decsribes two relatively simple molecular processes, an auto-catalytic system, and a system of self assembly. Together their produce a capacity for self-repair. Auto-catalysis is a generative process of local asymmetry, but this process will dissipate (due to the 2nd law) if not somehow contained. The self-assembly process can build shells (or membranes). The self-assembly of a shell is dependent on a local asymmetry of molecules (that is it's constraint. The auto-catalytic process is dependent on some type of physical containment to persist (thus the shell produced through the process of self-assembly serves as it's constraint). In effect the resulting system composed of these two process is able to maintain itself because each produces constraints the other needs. The sub-processes are complementary and inter-dependent.
The type of emergence Deacon has just described fits under the 3rd category bulleted at the top of this post. A novel property (persistence through self-repair) has emerged. One could imagine this theory of complementary and inter-dependent process nesting forward in complex loops until the constraints in the form of information become retained in a stable form like DNA. As each new loop of added inter-connected complexity unfolds a new type of causality emerges into the world. Eventually organisms with nervous systems emerge, and finally those with minimal the higher degrees of sentience.
I think this is a beautiful theory. It is reductive in the sense that its process is simple (perhaps even fundamental), yet the theory can in principle be applied efficiently across many progressions of emergence. Where along this chain, function, meaning, consciousness and purpose emerge are exceedingly difficult questions not soon to be answered in any definitive way. Yet I think this principle of complementary inter-dependent constraints (my phrase) points to a fruitful direction to explore. I also feel it has utility in the mean-time both as a guide for introspection and scientific hypotheses. As Deacon puts it 'life is constantly in the process of changing its own boundary conditions' to me this suggests freedom has evolved through it's dependence on constraint.
While Deacon was heavily influenced by Charles Peirce, it should be evident that his approach aligns nicely with the insights of eastern thought that have been around for over 2,500 years. In his book Incomplete Nature: How Mind Emerged from Matter Deacon begins with a reference to chapter 11 of the tao te ching which speaks to the utility of emptiness.
Back to the video, Dan Dennett voices agreement with the thrust of Deacons approach, Rosenberg unsuprisingly is not. There is a strong hesitancy within the group to let go of the conception of fundamental levels as it applies to 'stuff'. The most vocal is Weinberg. The thrurst of his argument is that while fermions and bosons are not an efficient (or in most even cases possible) means to understand higher level properties, they are still fundamental because they 'entail' the higher level properties (in principle).
Pigliucci asks Weinberg what it is that justifies that belief. Weinberg a Nobel prize winner appeals to historical successes in physics and cites phase transitions. Through statistical dynamics approximations of thermodynamics can be obtained from the level of fundamental particles. Those approximations however, rely on boundary conditions (like temperature and pressure I think) which are properties of the higher level. This is pointed out by Pigliucci at about the 52 minute mark of the video, There is consensus that all higher level phenomena are compatible with the sub-atomic level but disagreement about whether 'entailment' should be implied. I believe this is the trap (bottom-up determinism) that Deacon is attempting to avoid.
Weinberg knows more about fundamental physics than perhaps anyone in the room (Carrol and Levin are also experts), and far more then I could ever hope to know. By listening to the discussion however, I am brought back to Rebecca Goldsteins introductory comments regarding our 'core intuitions'. They are extremely hard to move and maybe especially so for experts. Of course Deacons approach is very much in line with my 'core intuitions' so it is easy for me to find value there, and potentially to miss the value in something Weinberg is advocating.
I think this argument is very important with regard to the future direction of science and if time avails I recommend listening to the entire video.
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