. Biophysics: concepts and mechanisms. Biophysics. 300 THE LANGUAGE AND CONCEPTS OF CONTROL some narrow field may each have rejected as noise some information border- ing on the subject which would be more pertinent to their discussions than either realizes. This is one of the reasons for disputes, sometimes very heated ones, between logicians who are specialized in different fields. Then of course there are man's errors in logic—and they are a fact too. Over even an hour's test, the adding machine will demonstrate man's errors in logic very vividly. We have seen that there is variation in nat
. Biophysics: concepts and mechanisms. Biophysics. 300 THE LANGUAGE AND CONCEPTS OF CONTROL some narrow field may each have rejected as noise some information border- ing on the subject which would be more pertinent to their discussions than either realizes. This is one of the reasons for disputes, sometimes very heated ones, between logicians who are specialized in different fields. Then of course there are man's errors in logic—and they are a fact too. Over even an hour's test, the adding machine will demonstrate man's errors in logic very vividly. We have seen that there is variation in nature. There is also order. There is variation in the physical structure of man's sensory organs. Therefore the nonverbal impressions which two men have of the same object may be quite different. The verbal impression each would give—thanks to training, experience, and definition—would, however, be about the same. It is gen- erally accepted that the essentials can be abstracted by one and com- municated to another by words. The variations can be described also, if they can be observed. Further, McCulloch and Pitts showed in a famous deduction that if anything can be described fully in words, the description can be programmed accurately into a man-made computer, provided the computer is comprehensive enough. Therefore our own "built-in" com- puter, as well as the man-made one, should have the physical capability to receive (as well as give) a complete description. Yet language has a drift in meaning over a course of time. Does the concept also drift? Feedback Control of a system by its computer is accomplished by feeding back into the controller the result of the measurement of difference or error (Figure 11-2). The computer can then dispatch the corrective order, the order which when carried out will reduce or eliminate the error. This is accomplished in mechanical and electrical machines through what is called a control am- plifier, a device which takes the deter
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