We have already described the constructs that go together to make up NPT. We've explained how NPT provides a set of tools that help us to understand and explain what goes on when we work to implement a new technology or other complex intervention. Because NPT is a formal theory - there's a logic to what a theory is and does - we want to provide some information about this too. NPT starts with the formal proposition that:

(a) Complex interventions become routinely embedded (implemented and integrated) in their organizational and professional contexts as the result of people working, individually and collectively, to implement them.

On the face of it, this doesn't seem remarkable. But it's important because it says that the routine embedding of a complex intervention is the product of action (the things that people do), not necessarily people's attitudes (how they feel about what they do), or their intentions (what they say they are going to do). Explaining implementation (process) and integration (structure) is about explaining action. So, to understand the embedding of a complex intervention we must look at what people actually do and how they work. In this context, the NPT proposes that:

(b) The work of implementation is operationalized through four generative mechanisms (coherence; cognitive participation; collective action; reflexive monitoring).

Here, NPT is concerned with identifying and understanding the ways that people make sense of the work of implementing and integrating a complex intervention (coherence); how they engage with it (cognitive participation); enact it (collective action); and appraise its effects (reflexive monitoring). These are expressed through organized and organizing agency, and the theory therefore proposes that:

(c)    The work of integration of a complex intervention requires continuous investment by people in ensembles of action that carry forward in time and space.

It is not enough to adopt and diffuse a complex intervention, people need to keep investing in it or it will atrophy. Continually investing in sense-making, commitment, effort, and appraisal is part of the routinization of a complex intervention. A complex intervention that is routinely embedded in practices ceases to be a 'complex intervention' at all, and instead disappears into the everyday world of normal activities, the things that people just get on and do. Normalization Process Theory focuses our attention down on how the work gets done - the everyday business of getting on with the job in hand - and the often very creative work that managers, professionals, patients and their families, do to normalize a set of tasks in a health care setting.