https://backofmind.substack.com/p/the-purpose-of-a-system-i…
https://backofmind.substack.com/p/the-purpose-of-a-system-is-you-cant
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I am, I think, finally realising that the “POSIWID” principle is more trouble than it’s worth. It’s a great slogan, and I don’t think I’m going to stop using it occasionally. But it seems to cause lots and lots of confusion, and if that’s what it does, then … well, it’s not really available to argue that this is unfair, or the fact that it’s systematically achieving a result other than the one intended can be ignored.
So I’m going to have one more go at explaining what POSIWID really means, then give up.
OK, to start with (and one of my main reasons for giving up on it), “The Purpose Of A System Is What It Does”, although it’s a fun thing to say, isn’t a fundamental principle of cybernetics at all. It is not even an axiom of Stafford Beer’s own model, the Viable Systems Model. What it is (as I started writing in a previous post) is a heuristic to try to explain to people how to draw the black boxes and go about applying the model.
It's important that this is a heuristic that’s only to be used in the context of something that’s at least potentially a viable system. So, for example, if you have an air conditioning unit that’s emitting black smoke, you can’t say “the purpose of this air conditioning unit is to emit black smoke”, because it’s not an ongoing system that’s going to be allowed to keep doing that. One of the big misconceptions that the POSIWID slogan fosters is that it should always be (but rarely is) mentally expanded to “the purpose of a system is what it systematically does, on an ongoing basis, with the permission of the other systems which form its environment”.
And that last clause about the other systems is really important. Immediately after coining the POSIWID phrase in Diagnosing the System, Beer emphasises that the “purpose” of the system you are analysing is always going to be a compromise with other systems in which it is embedded.
So, for example, a (kind and clever) reviewer of my book applied the principle to his train journey and concluded…