#EssentialVariable

According to #WRAshby, #Regulation is blocking the flow of #Variety from the (environmental) #Disturbance to the (internal, #System protected) #EssentialVariable. There are two primary forms of blocking the effect of the disturbance on the system:
Passive (by sheltering from), and
Active (on par with)
From:
W. Ross Ashby (1956) - An Introduction to Cybernetics, (Chapman & Hall, London) - available electronically from:
http://pespmc1.vub.ac.be/ASHBBOOK.html