When Beers says:
> According to the cybernetician the purpose of a system is what it does...
The "according to the cybernetician" part makes it pretty clear that we're now entering some kind of abstract space that cares not for the stated intentions of humans. It seems that what's "very hot right now" is to ignore the first part.
I think it's an especially reasonable position to take when the system in question has no designer to disagree with anyhow.
> we're now entering some kind of abstract space that cares not for the stated intentions of humans
But that's the thing about systems: they may involve humans but they don't necessarily reflect the intentions of the individual humans involved. Even when a system is created with a stated intent (i.e. for a stated purpose) that doesn't mean it will actually behave in a way that aligns with this intent. Logically you then shouldn't take the human intent into consideration when analyzing a system's actual effects and outcomes (except to determine whether it aligns with those but that's secondary).
IOW the purpose of a system (i.e. "what it exists for") can be different from the purpose for which it was created (i.e. "what it is meant to do"). I guess "purpose" in this case is an overloaded term because the former more uses a meaning that more closely aligns with "function" (like the function of a predator in an ecosystem may be controlling prey population but that doesn't suggest intent nor design) and the latter uses a meaning that more closely aligns with "intent" (like during wildfires controlled burns are performed with the intent of stopping the spread of the wildfire).
But I'd say it's a stretch to apply this to statements like "the purpose of organisms is to increase entropy" because that strongly implies intent rather than function (because the latter could also be simply expressed as "organisms create entropy").
POSIWID is usually the end result of asking some basic questions about "A System":
For organisms, sometimes just asking it directly can give more useful answers (or surprises,YMMV)Not necessarily. Cybernetics was specifically the study of systems, so that part can also be taken as an appeal to the experts in the matter.
Generally the point of this observation is specifically about human systems, either designed or evolved. The observation stems from the fact that it's (a) impossible to ascertain what the true intention of a human that designed a system was (they may be publicly lying about it, or even privately, it even to themselves), and (b) any complex enough system has been influenced and possibly "warped" by many more than one human, so the original unique intention, whatever it was, isn't the sole guiding principle behind it.
So, if analyzing a system, rather than trying to dig into its creators' history or anything like that, it's best to just look at what the system is doing and consider that its true current purpose.