One converse of POSIWID - when you find a purpose surviving, look for the system whose purpose it is. Nothing happens by accident.
When used casually, this leads to wild conspiracy theories. Various imaginary purposes may be served by the death of a rich young woman in a Paris subway - therefore some agency must have planned this event to serve one of these purposes.
The trouble with this approach is that it doesn't allow us to discriminate between alternative explanations. Any given event may have a vast number of different consequences for different people. How do we decide which of these consequences to elevate to the status of "purpose"? Was the death planned to allow some middle aged man to marry his mistress, or to sell newspapers, or to distract the public from some other matter, or what?
Make your own conspiracy theory ...