(2024-07-10) Davies The Purpose Of A System Is You Cant Always Get What You Want

Dan Davies: the purpose of a system is you can't always get what you want. The “POSIWID” principle is more trouble than it’s worth

So I’m going to have one more go at explaining what POSIWID really means, then give up.

isn’t a fundamental principle of cybernetics at all.

heuristic to try to explain to people how to draw the black boxes and go about applying the model.

only to be used in the context of something that’s at least potentially a viable system

“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”.

Immediately after coining the POSIWID phrase in Diagnosing the System, Stafford 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.

POSIWID is not meant to be a claim about the universe – it’s a heuristic for deciding what information needs to be taken into account. The whole business of cybernetic, and any other kind of, modelling is to decide what features of the world you’re going to pay attention to and ignore

So, “the purpose of the rail network is to disincentivise people from making train journeys”, true or not? Well, in my view more true than not true, but you have to be super clear what system you are analysing

each individual train is embedded in a system which has the purpose of “run the timetabled journeys safely”, which in turn is embedded in a system with the purpose “set a timetable consistent with the available resources”, which is embedded in a system to “balance the demand for rail travel with the politically sustainable subsidy”. (games theory)

the part of the rail network you interact with has to compromise its own priorities with those of the higher levels

I think it’s right to say that the purpose of the consumer-facing part of the system is to act as a rationing system for rail journeys.

Which affects the kind of information you might consider relevant to collect in analysing that system

For one thing, if you understand that the British rail system is a rationing system, you’ll be less inclined to compare the cost of a journey from Cardiff to London with a journey from Brest to Paris