William T. Powers
Many people have some sense of what control is about, but very few understand clearly how control works and even fewer (including control engineers) understand clearly what a control systems controls: Not “output” or “action” but perception of whatever is being controlled; that which action accomplishes. When you stop to think about it, you realize that a control system knows nothing about output or actions; it “knows” only what it senses. The distinction may seem trivial, but the consequences are profound. Bill Powers puts it all in context.