When foresight seems impeccable, things still go wrong. Why?

Purpose – This article seeks to provide a systematic examination of the unanticipated results following the introduction of various types of new policy, process, design, product or service. Design/methodology/approach – A rough taxonomy categorizes the generic kinds of unintentional consequences. Findings – Careless political, technical, commercial, military or even personal decisions often underlie the most problematic of secondary effects. Originality/value – Unscheduled second‐ or third‐order effects have often been attributed to a “law” governing such phenomena. Although no such law exists, there exist indeed the unwanted effects – and sometimes on a grand scale, too often a bane of humankind.