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In today’s post, I am looking at constraints with respect to Cybernetics. I am looking mainly at the ideas from Ross Ashby, one of the pioneers of Cybernetics. Ashby wrote one of the best introductions to Cybernetics, aptly titled An Introduction to Cybernetics. Ashby described constraints in terms of variety. Variety is the number of distinct elements that an observer is capable of making. For example, consider the following set of elements:

Someone could say that the variety of this set is 3 since there are three letters. Some other person could say that the variety is actually 5 if the lower and upper cases are distinguished. A very common example to explain variety is a traffic stop light. Generally, the stop light in the US has 3 states (Red, Yellow and Green). Sometimes, additional states are possible such as blinking Red (indicating a STOP sign) or no light. Thus, the variety of a stop light can vary from 3 to 4 to 5.

Ashby explained constraints as – when there are two related sets and one set has less variety than the other, we can determine that a constraint is present in the set of elements with less variety. Let’s consider the stop light again. If all the lights were independent, we can have 8 possible states. This is shown below, where “X” means OFF and “O” means ON.

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