The concept of system is central to any discussion of organisation; few managers, perhaps, would think of that concept exactly as a tool. It is, they might consider, a term to be defined, and then to be properly used. In Chapter One, however, we begin to probe the connotation of the word ‘system’. The target definition turns out to be elusive. It seems more important to recognise that we are handling a conceptual tool, because a tool has to be understood in terms of its capability to facilitate the work undertaken, and also in terms of the limitations that its own shortcomings (in this case of reliable definition) impose on that work. In an effort to elucidate all this, the chapter engages in some mental exercises intended to loosen-up rigid attitudes to whatever is systemic about enterprises, and to promote an enquiry rather than a didactic ethos for the whole book. The examples are exclusively managerial, and deal with both economic and human affairs.