The Law of Requisite Variety
Variety and interconnectedness are among the necessary ingredients that allow a system (a society, an animal, a political party, etc.) to survive and thrive in a variety of environments, including those generated by human activity. Ross Ashby, who was one of the founding fathers of cybernetics, recognised their importance when he proposed his Law of Requisite Variety.
His law says, in brief, that regulation is possible only if the regulating system is as various and flexible (responsive to changes) as the system to be regulated.
An informal statement of this law, attributed to Ashby, is:
If you can describe complexity, then it’s not complex any more.
Rosalind Armson expands on the formal law as follows:
"When a system, such as a human being, is exposed to perturbations in its environment, it may have a number of responses. These responses lead to a number of possible outcomes. Of all the possible outcomes, only some will be ‘acceptable’ in terms of the system’s purpose or survival. This is as true of organisations, baggage-handling systems, telephone-enquiry systems and other purposefully-interconnected systems as it is of humans and their society. In practice, the Law of Requisite Variety says that, in order to fulfil its purposes and survive, the system must be capable of a greater variety of responses than the variety of perturbations in the environment. The fewer the number of acceptable outcomes, then the more the variety of possible responses must exceed the variety of perturbations. The system then has requisite variety – the variety it requires to survive and fulfil its purpose.
Armson goes on to celebrate complexity:
The very human variety that can be so infuriatingly difficult to understand is the variety that enables the human-person system to survive in an environment that also exhibits astonishing variety. Returning to the context of systems thinking, and the significance of bringing all my human variety to situations I perceive as complex, I need to be capable of variety in my thinking, actions and emotions to respond appropriately to the complexity I perceive in the messy situation. This is what Ashby meant by requisite variety.
While I bring requisite variety to the task of improving a messy situation, I find myself asking, ‘How can I be sure I am not contributing to the process that keeps the mess in place?’ ‘How can I be sure that some of my variety of actions, thinking and emotions is not getting in the way of improving the situation?’ I am thinking here of my confusions, prejudices, preferences, entanglements and blind spots. These too are manifestations of my variety and, unless I can account for them in some way, they can make the situation even more difficult to understand than it was before. I need awareness of how I interact with situations that I am trying to improve. This means I have to be aware of how I see the situation (my perspective ); how I understand the situation; how I distinguish systems within it; how I communicate my understandings to other stakeholders; how I act in it; how I see and recognise the outcomes; and how I evaluate the outcomes."
Rosalind Armson - Growing Wings on the Way