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

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.

A rough taxonomy categorizes the generic kinds of unintentional consequences.

Careless political, technical, commercial, military or even personal decisions often underlie the most problematic of secondary effects.

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.