Saturday, 16 July 2016

Ashby on Object, System and Complexity

These quotes are from a paper by George Klir called "W. Ross Ashby: a pioneer of systems science", International Journal of General Systems, vol. 38, no. 2, 2009.

System and Object:
At this point we must be clear about how a 'system' is to be defined. Our first impulse is to point at the pendulum and to say, the system is that thing there. This method, however, has a fundamental disadvantage: every material object contains no less than an infinity of variables and therefore of possible systems. The real pendulum, for instance, has not only length and position; it has also mass, temperature, electric conductivity, crystalline structure, chemical impurities, some radioactivity, velocity, reflecting power, tensile strength, a surface film of moisture, bacterial contamination, an optical absorption, elasticity, shape, specific gravity and so on and on. Any suggestion that we should study ‘all’ the facts is unrealistic, and actually the attempt is never made. What is necessary is that we should pick out and study the facts that are relevant to some main interest that is already given ... The system now means, not a thing, but a list of variables.  (Ashby, An Introduction to Cybernetics - 1956)
George Klir comments on this definition that:
It is rather surprising and, in my opinion, unfortunate that the fundamental difference between these two concepts, those of an object and a system, is still not properly appreciated. Yet, it is a difference which is at the very heart of systems science. Confusion arises when this difference is not recognised and, as some critics suggested, systems science becomes then the study of everything (every object) and is thus logically empty. 
Yes. If Systems Theory is seen as a theory of objects and not systems, it inevitably states empty metaphysical propositions. I think the logic and coherence lies in the distinctions which are made.

The word ‘complex’, as it may be applied to systems, has many possible meanings, and I must first make my use of it clear. There is no obvious or preeminent meaning, for although all would agree that the brain is complex and a bicycle simple, one has also to remember that to a butcher the brain of a sheep is simple while a bicycle, if studied exhaustively (as the only clue to a crime) may present a very great quantity of significant detail. Without further justification, I shall follow, in this paper, an interpretation of ‘complexity’ that I have used and found suitable for about ten years. I shall measure the degree of ‘complexity’ by the quantity of information required to describe the vital system. To the neurophysiologist the brain, as a feltwork of fibers and a soup of enzymes, is certainly complex; and equally the transmission of a detailed description of it would require much time. To a butcher the brain is simple, for he has to distinguish it from only about thirty other ‘meats’, so not more than log2 30, i.e., about five bits, are involved. This method admittedly makes a system’s complexity purely relative to a given observer; it rejects the attempt to measure an absolute, or intrinsic, complexity; but this acceptance of complexity as something in the eye of the beholder is, in my opinion, the only workable way of measuring complexity. (Ashby, 1973 - "Some peculiarities of Complex Systems", Cybernetic Medicine, Vol 9, no. 1)

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