bnevin@CCH.BBN.COM (Bruce E. Nevin) (06/20/88)
Date: Fri, 17 Jun 88 08:42 EDT From: Bruce E. Nevin <bnevin@cch.bbn.com> Subject: determinism a dead issue? To: ailist@ai.ai.mit.edu cc: bn@cch.bbn.com Is the notion of determinism not deeply undercut by developments in study of nonlinearity and Chaos? There is sufficient nonlinearity in the workings of brains, bodies, and interacting agents in the world to ensure that simple billiard ball click click click in the pocket determinism is not even an approximation. There seems to me a parallel to Bateson's discussion of creatura vs pleroma, terms borrowed from Jung. If I remember correctly which is which, creatura is the deterministic cause-effect realm amenable to description in simple, linear, Newtonian terms; pleroma (the term derives from a root having to do with "fullness", as in "plenary session") involves metabolism, where outputs are not directly predictable from inputs in terms of forces and impacts and what Bateson elaborates as "cybernetic explanation" applies. He argued that imagery of forces and impacts were inappropriate for most of what is important to us. He was not aware of or at any rate did not write about the relationship of this to nonlinearity and chaos before his death. What is the relationship between the two? Is it the case that systems involving nonlinearity always involve feedback or feedforward loops? My impression from reading is yes. (Isn't it mutual effect of the values of two or more variables on one another that makes an equation nonlinear, and isn't that a way of expressing feedback or feedforward? The effect of friction in a physical system varies according to velocity, even as it affects velocity.) Is it the (stronger) case that systems with such cybernetic loop structure always involve nonlinearity? No, computers are generally advertised as deterministic. Is it that nonlinear systems are not error correcting? Or perhaps that they are analog rather than digital systems? Are massively parallel systems nonlinear, or do they tend to be? Does the distinction apply to now familiar characterizations of brain hemisphere specialization? This has relevance to how an AI based on deterministic, linear systems can do what nonlinear organisms do. Bruce Nevin bn@cch.bbn.com <usual_disclaimer>