Approaches to safety have often considered the “human” factor in an organisation or operation as a major contributor to unwanted outcomes. The view of “human” as a problem leads to responses that involve trying to exert more control over people. While these may make intuitive sense for some, research suggests that such a view may not be valid as there are an enormous number of other factors (many of which are beyond control of the human at the sharp end) that are behind the creation of success and the occasional failures. This chapter begins with a review of normal accident theory, before using complexity science to fill out the problematic nature of the notion of “human error”. It then discusses one of the prominent problems associated with complexity, safety drift. Lastly, this chapter looks at various proposed solutions (e.g. resilience engineering) by which a healthcare system can manage complexity and perhaps reduce the potential harm to patients.