bohm2 said:
Davies seems pretty skeptical about 'downward causation' within present-day physics:
In fact, the problem is really that he sees it as "trivial" - so obvious that you have to wonder what the fuss is about.
Davies: Sometimes physicists use the language of whole-part causation for ease of description. For example, a ball rolling down a hill implies that each of the ball’s atoms is accelerated according to the state of the ball as a whole. But it would be an abuse of language to say that the rotating ball caused a specific atom to move the way it did; after all, the ball is the sum of its atoms. What makes the concept ‘ball’ meaningful in this case is the existence of (non-local) constraints that lock the many degrees of freedom together, so that the atoms of the ball move as a coherent whole and not independently. But the forces that implement these constraints are themselves local fields, so in this case whole-part causation is effectively trivial in nature. Similar remarks apply to other examples where ‘wholes’ enjoy well-defined quasi-autonomy, such as whirlpools and electric circuits.
The situation is different again in the case of spontaneous self-organization, such as the Bénard instability, or the laser, where atomic oscillators are dragooned into lockstep with a coherent beam of light. But even here, the essential phenomenon can be accounted for entirely in terms of local interactions plus non-local constraints.
This is the essence of it. Downward causality is "just constraints". And they "emerge" though bottom-up construction. All they actually do is limit local degrees of freedom. So big deal.
Yet then this understanding about causality leads on to things which are a big deal. For a start, it says that localised properties or other forms of local definiteness have to actually undergo a history of development. And then, logically, they have to be in turn the kinds of local properties/entities that continue to construct the globally prevailing set of constraints. It is a mutally complementary story. The whole has to make the parts that make the whole that makes the parts, etc.
So instead of the usual ontology of an existence that just exists, we have a system that self-organises through the interaction of global constraints and local degrees of freedom. Physically, that is a very different picture of reality. The material atoms and the formal laws of physics have to arise co-operatively, via their mutually self-causing interaction.
It also then leads on to a proper analysis of complexity as systems that can construct their own local constraints (again, the epistemic cut issue of various forms of information - genes, words, membranes, pores, etc - being able to create non-holonomic constraints that limit ordinary material processes, Pattee's rate dependent dynamics).
Davies: In a sense, global principles may be said to emerge from local physics, but most physicists see things the other way round, preferring to regard global principles as somehow more fundamental.
This is the mistake - to seek to make one aspect of systems causality more fundamental than the other. What is fundamental is instead the dichotomy, the fact that you have two kinds of cause that are mutually exclusive and exhaustive in interaction. Each is creating its other (so that it can itself be created). A virtuous circle in which both the local and the global are matchingly fundamental.
Davies: Let me know turn to the other sense of downward causation: the relationship between different conceptual levels describing the same physical system. In common discourse we often refer to higher levels exercising causal efficacy over lower. For example, mind-brain interaction: ‘I felt like moving my arm, so I did.’ Here the mental realm of feelings and volitions is expressed as exercising causal efficacy over flesh. Another example is hardware versus software in computing. Consider the statement: ‘The program is designed to find the smallest prime number greater than one trillion and print out the answer.’ In this case the higher-level concept ‘program’ appears to call the shots over what an electronic gizmo and printer and paper does.
Here, Davies slips into treating downward cause (limiting constraints) as now a variety of upward cause (material construction, deterministic action, effective cause).
It is confusing as it is possible for this kind of material/effective cause to pop out at higher levels of hierarchical organisation. We can talk about new properties emerging that "do things" in the sense of locally making something happen (rather than globally limiting such degrees of freedom).
But this is no longer talking about downward causation. It is talking about upward causation at a higher scale of description. The two concepts
must be kept separate.
So the naive folk psychology description of a movement of the arm is that there is an "I" who felt like doing it. A neuroscience description would instead look for a set of constraints (some global attentional/intentional state) in interaction with some set of local degrees of freedom (all the memories and habits involved in constructing a movement such as moving an arm).
Davies: A more dramatic example of mind-brain causation comes from the field of neurophysiology. Recent work by Max Bennett (Bennett & Barden, 2001) in Australia has determined that neurones continually put out little tendrils that can link up with others and effectively rewire the brain on a time scale of 20 minutes! This seems to serve the function of adapting the neuro-circuitry to operate more effectively in the light of various mental experiences (e.g. learning to play a video game). To the physicist this looks deeply puzzling. How can a higher-level phenomenon like ‘experience,’ which is also a global concept, have causal control over microscopic regions at the sub-neuronal level? The tendrils will be pushed and pulled by local forces (presumably good old electromagnetic ones). So how does a force at a point in space (the end of a tendril) ‘know about,’ say, the thrill of a game?
There are just so many examples like this from neuroscience. Globally a constraint is formed (master this game) and locally this shapes up the habits/memories needed to construct the capacity for such action. The ends produces the means.
Davies: Information enters into science in several distinct ways. So far, I have been discussing the wave function in quantum mechanics. Information also forms the statistical basis for the concept of entropy, and thus underpins the second law of thermodynamics (information should not come into existence in a closed system). In biology, genes are regarded as repositories of information – genetic databanks. In this case the information is semantic; it contains coded instructions for the implementation of an algorithm. So in molecular biology we have the informational level of description, full of language about constructing proteins according to a blueprint, and the hardware level in terms of molecules of specific atomic sequences and shapes. Biologists flip between these two modes of description without addressing the issue of how information controls hardware – a classic case of downward causation.
Fortunately some biologists do address this question.
Those that are systems scientists and familiar with the epistemic cut, semiosis, and other such expanded models of causality.
Davies: Most physicists are sceptical of downward causation, because they believe there is ‘no room’ in existing theories of causation for additional forces.
And they would be correct in that downward causation is not about "forces" (local material effective cause) but strictly only about global constraint (formal and final cause).
Davies: Another way to escape the strictures of causal closure is to appeal to the openness of some physical systems. As I have already stressed, top-down talk refers not to vitalistic augmentation of known forces, but rather to the system harnessing existing forces for its own ends. The problem is to understand how this harnessing happens, not at the level of individual intermolecular interactions, but overall – as a coherent project. It appears that once a system is sufficiently complex, then new top-down rules of causation emerge.
This is repeating the mistake of trying to make one pole of a dichotomy more fundamental than the other (when each has to be fundamental as the definition of either pole has to be both complementary and mutually exclusive).
So a systems view is closed in the sense that both the local and global are equally fundamental. But also both emerge, because they emerge from each other. So in another sense, this is an open, developmental view.
That is why systems thinking is based on Peirce's notion of vagueness (and Anaximander's notion of the apeiron). Everything emerges. But the only possible results are dichotomistic. The only system that can develop is one that is self-making in that its locally constructing degrees of freedom are of the kind that can make (and in return, be made by) some prevailing, coherent, network of constraints.
Davies: A possible solution of the cosmological constant problem comes from top-down causation. Suppose this quantity, normally denoted Λ, is not a constant at all, but a function of the total amount of information that the universe has processed since the beginning.
This is an excellent concrete example of how a different systems model of causality can underpin new physics.
Davies: My suggestion is to take downward causation seriously as a causal category, but it comes at the expense of introducing either explicit top-down physical forces or changing the fundamental categories of causation from that of local forces to a higher-level concept such as information.
As said, downward causation is about constraint and should not be conflated with the idea of "some kind of higher level force". Nor is it more fundamental than local forces, or bottom-up material/effective causation.
So yes, take downward causation seriously. But see it as a "different but mutual" form of causation - the missing half of the current story.
It is just exactly what Davies starts out as describing as "trivial" because it is so obvious. But the consequences of taking it seriously are not trivial.
