Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!bbn.com!archive.bbn.com!aboulang From: aboulang@bbn.com (Albert Boulanger) Newsgroups: comp.ai.philosophy Subject: Re: Emergent Properties Message-ID: Date: 10 Nov 90 16:50:38 GMT References: <1990Oct12.214636.7945@ncsuvx.ncsu.edu> <30@tdatirv.UUCP> <1990Oct19.201604.7280@ncsuvx.ncsu.edu> <3369@aipna.ed.ac.uk> <1990Oct26.214354.11063@ncsuvx.ncsu.edu> <3383@aipna.ed.ac.uk> <1990Oct31.001104.22908@ncsuvx.ncsu.edu> <1990Oct31.102704.18335@csc Sender: news@bbn.com Reply-To: aboulanger@bbn.com Organization: BBN, Cambridge MA Lines: 102 In-reply-to: csmith@cscs.UUCP's message of 5 Nov 90 02:11:35 GMT In article <1990Nov5.021135.3749@cscs.UUCP> csmith@cscs.UUCP (Craig E. Smith) writes: It is possible that my idea of the definition of emergence is off, because I base it only on things I have seen people say here in recent postings. If so what is your precise definition of emergence, and emergent properties? It seems to me that you are implying exactly what I said, that calling something an emergent property is only saying that you don't know how it works, or are unable to adequately describe it. Is emergence simply a standard term used to describe something not yet understood, or is it something more? Just because you cannot understand something doesn't mean it is mystic. It only means you are not omniscient. It doesn't make me very uncomfortable that their are things which we cannot explain, although I would like to have an explanation for everything. As much as we may dislike the fact, the human brain is finite, and has a limited capacity for understanding, and processing information, even when assisted by a computer. Many of the things that we now think of as emergent will later be explained, and thus become non-emergent, while others will never be explained, and will remain emergent. I don't think this should necessarily have any affect on the general advancement of science, and I don't see where anything you have said contradicts my statement. To recap what I have been presenting in prior messages, I have claimed that the notion of emergence is best understood in the context of nonlinear dynamical systems. Emergence is fundamentally due to the fact that nonlinear systems do not obey the principle of superposition that is in the core of the analysis of linear systems. This is the basis of understanding emergence. In this note, I will mention some other properties of nonlinear dynamical systems that will sharpen our view of what emergence is and hopefully show that it is not just "a standard term used to describe something not yet understood" - yet in a way it is just that. (The ole' objectivist debate ;-)) This is fundamentally due to a kind of uncertainty principle arizing from the sensitive dependence of initial conditions in chaotic dynamical systems. In fact, it may explain a long standing problem in physics - the "emergence" of an arrow to time from a microscopic universe of reversible laws. Since we are also looking at many-body systems, we will also have to throw in some themodynamics. One way to measure emergence of structure is to take on an information-theoretic approach and look at the "entropy" of a system. (One has to be careful in the formulation of entropy under these conditions) If the measure of information increases, then we have new structure being formed. First of all this implies that a many-body system under investigation is not in thermodynamic equilibrium -- "Self organization under far-from-equilibrium conditions". The tools for analyzing such nonequilibrium systems is also relatively recent and goes hand in hand with results from nonlinear dynamics -- the joint area is known as ergodic theory. The picture one should have then is a many-body system with nonlinear interactions in a heat-bath (a source for energy and some place to discharge heat). One reference on nonequilibrium thermodynamics is: "From Being to Becomming: Time and Complexity in the Physical Sciences" Ilya Progigine W.H. Freeman & Co., 1980 One necessary but not sufficient sign of chaos in a nonlinear dynamical system is the existance of sensitive dependence on initial conditions. What happens is that nearby initial trajectories undergo an exponential expansion. Any uncertainty in initial conditions are amplified exponentially. Another necessary condition for chaos is a measure of the rate of expansion of the axis of the hyperelipse formed by a small initial point set. If one of the so-called Lyapounov exponents is > 0, (a log is taken -- also one sees many spellings for Lyapounov) then you have a necessary condition for chaos. Consider what happens when you put such a chaotic non-linear many-body system in a heat-bath. What can happen is that the system will pick up small pertubations on the heat bath at the microscopic level and amplify them to the level of "emergence" of structure on the marcoscopic level. We can not in *principle* know what these pertubations are! This approach has been written up in several papers: "Chaos, Entropy, and the Arrow of Time" Peter Coveney New Scientist, 29 September 1990, 49-52 This one has minimal math. "The Second Law of Thermodynamics: Entropy, Irreversibility, and Dynamics" Peter Coveney Nature, Vol 333, 2 June 1988, 409-415 "Stange Attractors, Chaotic Behavior, and Information Flow" Robert Shaw Z. Naturforsch, 36a, 1980, 80-112 This in my view, is the mechanism for the the evolution of life from an non-life protoform. I also think it is fundamental reason of why "open" computational systems can be so powerful -- people in the open systems game need to take a dynamical systems view of what they are doing. I normally botch up my presentations by being too brief so if anybody needs more unpacking, give a holler. Regards, Albert Boulanger aboulanger@bbn.com