W. Ross Ashby’s An Introduction to Cybernetics advances a foundational proposition: cybernetics is not primarily the study of mechanical objects, but of regular behaviour, communication, and control wherever they appear—in animals, machines, brains, societies, or economies. Following Wiener’s definition of cybernetics as the science of “control and communication”, Ashby deliberately detaches the field from electronics and advanced mathematics, arguing that its principles can be built from simple concepts such as change, transformation, stability, feedback, information, and regulation. His method is radically functional: cybernetics does not ask what a thing is made of, but what it does, how it changes, how it responds to disturbance, and how its possible states are constrained. The book’s structure makes this intellectual architecture explicit: Part I develops mechanism through transformation, determinate machines, feedback, stability, and the black box; Part II analyses variety, transmission, entropy, and noise; Part III applies these concepts to biological regulation, requisite variety, error-controlled regulators, and the amplification of control. A specific case is Ashby’s treatment of complex systems such as the brain or society, where traditional reductionist methods fail because changing one factor alters many others. His conclusion is therefore decisive: cybernetics offers a common language for understanding complexity, showing that effective regulation requires sufficient variety to match disturbance and that control is achieved through organised relations rather than material substance.