Fundamental notions concerning cybernetics, as derived from the systematic application of logic to questions of communication and control, are illustrated. Particular attention is given to the concepts of "system" "structure" and "dynamics" and it is shown that these concepts ensure that better and more exact understanding and forecasting of reactions in organised beings can be obtained. Turing to hypnosis, it is made clear that a trance is the execution of a momentarily proposed programme; it is not the result of a generalised mechanical action, but is preordained and geared to various situations. The difficulty that the hypnotised subject finds in aciting against his own interests, or against moral priniciples, can be seen, for example, as a consequence of pre-programming. Another result is given moment and a given type of person. Since cybernetis has proved useful in psychology, the hope is expressed that it can be included as a teaching subject for those who learn, practise and teach hypnotism.