Systems don't appreciate being fiddled and diddled with. They will react to protect themselves.
Systems tend to oppose their own proper functions.
Perfection of planning is a symptom of decay.
People in systems do not do what the system says they are doing.
The system itself does not do what it says it is doing.
To those within a system, the outside reality tends to pale and disappear.
Specialized systems select for specialisation.
A complex system that works is invariably found to have evolved from a simple system that worked.
Experience isn't hereditary - it ain't even contagious.
The meaning of a communication is the behaviour that results.
Information theory is a mathematical treatment of what is left after the meanings have been removed from a Communication.
Just calling it "feedback" doesn't mean that it has actually fed back. To speak precisely: It hasn't fed back until the system changes course. Up until that point it's merely sensory input.
Most of the parts are needed primarily as correctives to the vicious tendencies of the other parts.