Today's work environments are getting ever more adaptive and dynamic. The underlying technologies are highly complex and distributed. As a consequence, both the theoretical fundaments and the methodological toolbox of Human Factors become challenged. By drawing on the field of production planning and scheduling (PPS) in manufacturing, this book is making explicit how Human Factors fails to fully account for many problems related to this type of environment. It is proposing a philosophical reorientation - based on critical realist thought - through a focus on agency and social structures as central concepts for the understanding of human behavior. The new ontological fundament then leads to the formulation of a critical realist theory/methods package for Human Factors. Through the integration of agency and social structure into our thinking about technology, Human Factors interventions will become more tuned to the networked and globalized work contexts we are increasingly engaged with.